FormulaEngineer

The Excel formula engine for .NET.
Create, read, recalculate and style .xlsx workbooks in C#.
No Excel install. No COM interop. Pure managed code.

Live demo · Functions · Validation · Examples · Styling · Pricing · Contact

An Excel dashboard generated by FormulaEngineer: a KPI band with revenue, cost and margin above a performance table with data bars and colour-coded status.

_{Generated in C#. No Excel, no COM, no template file.
29 live formulas · 18 format rules · 25 merged ranges · 36 styles from 9 fonts · 13.7 KB}

_{↓ Download this workbook}

1. Introduction

FormulaEngineer is a complete .NET Excel solution for creating, reading, recalculating, and professionally styling .xlsx workbooks.

Most .NET spreadsheet libraries can open and create Excel files. Very few can accurately evaluate the formulas inside them.

FormulaEngineer was built around that gap.

It parses Excel formulas, resolves workbook references and dependencies, applies Excel-style type coercion and error behavior, and calculates fresh results in pure managed .NET—without starting Excel or relying on COM automation.

Since version 3.0, FormulaEngineer also provides a comprehensive workbook-presentation API for producing polished reports, financial models, exports, and dashboards.

Why recalculation matters

An .xlsx workbook may contain formula results previously saved by Excel. These cached values can be missing, stale, or incorrect after an application changes the workbook inputs.

FormulaEngineer evaluates the workbook logic directly.

Cached value stored in file
            │
            ├── Input changes
            │
            ▼
Cached result may now be stale
            │
            ▼
FormulaEngineer recalculates the formula
            │
            ▼
Fresh calculated result

Reading a cached value is not the same as recalculating a formula.

2. Why FormulaEngineer?

Real formula evaluation

FormulaEngineer does not merely read the last result saved inside an .xlsx file. It reads and evaluates the formula itself.

461 Excel-compatible functions

FormulaEngineer supports modern and classic Excel functions across lookup, financial, statistical, engineering, text, date/time, logical, database, dynamic-array, and lambda-helper families.

Excel-style workbook behavior

Formula evaluation includes references, ranges, structured tables, spilled arrays, type coercion, dependency resolution, and Excel error propagation.

High-performance streaming I/O

The forward-only reader and writer are designed for predictable memory usage, from small business reports to large server-generated exports.

Complete workbook presentation

Create workbooks that people can open and use immediately—with styling, conditional formatting, tables, comments, images, shapes, charts, sparklines, and auto-fit.

Cross-platform and server-ready

Run FormulaEngineer in ASP.NET Core, background services, Docker containers, CI/CD pipelines, Azure Functions, AWS Lambda, Windows, Linux, and macOS.

3. Key capabilities

Accurate formula evaluation — verified against hundreds of real-world formulas and workbook scenarios.
461 Excel-compatible functions — across all major business and technical formula families.
Modern dynamic arrays — including FILTER, SORT, SORTBY, UNIQUE, SEQUENCE, TAKE, DROP, HSTACK, and VSTACK.
Lambda helpers — including LET, LAMBDA, MAP, REDUCE, SCAN, BYROW, BYCOL, MAKEARRAY, and ISOMITTED.
Advanced lookup behavior — including XLOOKUP, XMATCH, VLOOKUP, HLOOKUP, INDEX, MATCH, approximate matching, wildcard matching, and reverse search.
Structured table references — including row-level calculated-column formulas.
Cross-sheet evaluation — formulas can reference values and ranges on other worksheets.
Dynamic-array spilling — with Excel-style broadcasting, spill references, #SPILL!, and #CALC! behavior.
Excel-style errors — errors such as #N/A, #VALUE!, #REF!, #NUM!, and #DIV/0! are preserved as calculation results.
Circular-reference detection — circular dependencies are detected instead of causing uncontrolled recursion.
Formula reading and writing — write formulas into cells, reopen the workbook, and evaluate them without Excel.
Streaming workbook I/O — forward-only reading and writing with a flat memory profile.
Professional styling — fonts, fills, borders, number formats, alignment, protection, merged cells, row heights, column widths, and auto-fit.
Advanced workbook objects — conditional formatting, rich text, named styles, themes, tables, notes, threaded comments, images, shapes, charts, and sparklines.
Cross-platform deployment — pure managed code targeting .NET 6 and later.

4. Package summary

Property	Details
Package	`FormulaEngineer`
Current version	`3.0.4`
Target framework	`net6.0`
Compatible runtimes	.NET 6 and later
Supported platforms	Windows, Linux, macOS
Excel installation required	No
COM interop required	No
Workbook format	Excel `.xlsx` / OOXML
Excel-compatible functions	461
Formula support	Read, write, and recalculate
Workbook I/O	High-performance streaming reader and writer
Presentation support	Styling, tables, comments, images, shapes, charts, and sparklines
Licence	Commercial with a 30-day free trial
Distribution	NuGet

5. Function coverage

FormulaEngineer supports 461 Excel-compatible functions and special forms across the major Excel formula families.

Family	Count	Coverage
Statistical	134	Aggregation, distributions, forecasting, regression, correlation, covariance, ranking, hypothesis testing, and legacy compatibility
Math and Trigonometry	72	Arithmetic, rounding, powers, factorials, combinatorics, trigonometry, hyperbolic functions, matrices, and random values
Engineering	50	Unit conversion, base conversion, bitwise operations, error functions, step functions, and complex numbers
Financial	45	Loans, investments, depreciation, securities, yields, cash flows, and rates
Text	42	Concatenation, searching, replacement, case conversion, parsing, splitting, and value-to-text conversion
Date and Time	25	Serial dates, business days, ISO weeks, date arithmetic, and month-end calculations
Lookup and Reference	20	Lookups, references, spill anchoring, range trimming, and address operations
Logical	20	Conditions, boolean logic, error handling, named values, custom functions, and lambda helpers
Information	20	Type checks, cell metadata, error inspection, and worksheet information
Dynamic Array	18	Generating, reshaping, filtering, sorting, stacking, wrapping, and transforming spilled arrays
Database	12	Criteria-based aggregation over structured data
Published total	461	Named functions and supported parser-level special forms

Popular supported functions

SUM · SUMIF · SUMIFS · COUNTIF · COUNTIFS · AVERAGEIFS

XLOOKUP · VLOOKUP · HLOOKUP · INDEX · MATCH · XMATCH

FILTER · SORT · SORTBY · UNIQUE · SEQUENCE · TAKE

PMT · PV · FV · NPV · IRR · XNPV · XIRR

DATE · EDATE · EOMONTH · WORKDAY · NETWORKDAYS

FORECAST.LINEAR · PERCENTILE.INC · STDEV.S · CORREL

LET · LAMBDA · MAP · REDUCE · SCAN · BYROW · BYCOL

Browse all 461 supported functions →

6. Excel-style formula behavior

Formula evaluation involves much more than parsing a formula string.

FormulaEngineer handles:

Cell and range references
Relative and absolute references
Cross-sheet references
Named references
Structured table references
Dependent formula cells
Numbers, text, dates, booleans, and blanks
Array broadcasting
Horizontal and vertical spilled arrays
Lookup matching and search modes
Excel serial-date calculations
Excel-style type coercion
Formula error propagation
Circular-reference detection

Formula results can include:

Result type	Examples
Numbers	Integers, decimals, percentages, and financial results
Text	Concatenation, lookup output, and formatted values
Dates and times	Excel serial dates and time values
Booleans	`TRUE` and `FALSE`
Blank values	Empty formula results
Spilled arrays	Horizontal and vertical dynamic arrays
Excel errors	`#N/A`, `#VALUE!`, `#REF!`, `#NUM!`, `#SPILL!`, `#CALC!`, and `#DIV/0!`

Excel errors are calculation results—not application crashes.

7. Validation

FormulaEngineer is validated with workbook-style scenarios—not only isolated parser tests.

Validation covers:

Surrounding worksheet data
Dependent formula cells
Cross-sheet references
Structured table references
Dynamic arrays and spilled results
Lookup formulas
Date and time formulas
Text formulas
Financial formulas
Statistical formulas
Excel error values
Cached values versus recalculated values

Representative validation scenarios

Scenario	Example formula	Verified behavior
Multi-level dynamic sort	`=SORT(A2:C13,{2,3},{1,-1})`	Sorts by category ascending and score descending
Unique two-level sort	`=SORT(UNIQUE(E2:F40,FALSE,FALSE),{2,1},{1,-1})`	Produces sorted unique name/product rows
Case-sensitive lookup	`=INDEX(D2:D20,MATCH(TRUE,EXACT(H2,A2:A20),0))`	Resolves the exact-case matching row
XLOOKUP with exact text	`=XLOOKUP(TRUE,EXACT(H2,A2:A20),D2:D20)`	Returns the value associated with the exact-case match
Closest-value lookup	`=INDEX(A2:A20,MATCH(MIN(ABS(C2:C20-H2)),ABS(C2:C20-H2),0))`	Finds the row closest to a target value
Dynamic sequence	`=SEQUENCE(5,1,10,5)`	Produces `10, 15, 20, 25, 30`
Sorted filtered results	`=SORT(FILTER(A2:B20,B2:B20>=LARGE(B2:B20,H2)),2,-1)`	Filters top records and sorts them descending
Structured reference	`=[@Price]*[@Quantity]`	Evaluates a calculated table-row formula
Excel error behavior	`=SEARCH(E2,A2)`	Returns `#VALUE!` when the text is absent
Error handling	`=IFERROR(SEARCH(E2,A2),"Not Found")`	Converts the error into the specified fallback

Test formula recalculation fairly

A fair formula-engine test should measure recalculation—not only cached-value reading.

Open a real workbook containing formulas.
Change one or more input cells.
Ignore the cached formula results stored in the workbook.
Recalculate the formulas.
Compare the newly calculated results with Excel.

Review the complete validation methodology →

8. Installation

Install FormulaEngineer from NuGet:

dotnet add package FormulaEngineer

Or add the package directly to your project file:

<PackageReference Include="FormulaEngineer" Version="3.0.4" />

FormulaEngineer targets .NET 6 and works with later compatible .NET versions.

The 30-day trial starts automatically on first use. No activation code is required during the trial.

9. Quick start

Create a workbook containing a formula

Formula text passed to ExcelFormula.From(...) must not include a leading =.

using FormulaEngineer.Api;

using (var writer = new ExcelWriter("sum.xlsx"))
{
    using (var sheet = writer.CreateWorksheet("Data"))
    {
        sheet.WriteRow(10);                              // A1
        sheet.WriteRow(20);                              // A2
        sheet.WriteRow(30);                              // A3
        sheet.WriteRow(ExcelFormula.From("SUM(A1:A3)")); // A4
    }

    writer.Close();
}

Open the workbook and evaluate the formula

using FormulaEngineer.Api;

using var reader = new ExcelReader("sum.xlsx");
using var evaluator = new ExcelFormulaEvaluator();
using var sheet = reader.OpenWorksheet("Data");

var result = evaluator.EvaluateCell(
    sheet,
    row: 4,
    col: 1);

Console.WriteLine(result);

Output:

The result is calculated from SUM(A1:A3). It is not simply read from a previously stored cached value.

10. Real-world invoice example

Create an invoice containing calculated line totals, subtotal, tax, and final total:

using FormulaEngineer.Api;

using (var writer = new ExcelWriter("invoice.xlsx"))
{
    using (var sheet = writer.CreateWorksheet("Invoice"))
    {
        sheet.WriteRow(
            "Item",
            "Qty",
            "Unit Price",
            "Line Total");

        sheet.WriteRow(
            "Widget",
            4,
            25.00,
            ExcelFormula.From("B2*C2"));

        sheet.WriteRow(
            "Gadget",
            2,
            80.00,
            ExcelFormula.From("B3*C3"));

        sheet.WriteRow(
            "Subtotal",
            "",
            "",
            ExcelFormula.From("SUM(D2:D3)"));

        sheet.WriteRow(
            "Tax (8%)",
            "",
            "",
            ExcelFormula.From("D4*0.08"));

        sheet.WriteRow(
            "Total",
            "",
            "",
            ExcelFormula.From("D4+D5"));
    }

    writer.Close();
}

Reopen the workbook and calculate the final total:

using FormulaEngineer.Api;

using var reader = new ExcelReader("invoice.xlsx");
using var evaluator = new ExcelFormulaEvaluator();
using var sheet = reader.OpenWorksheet("Invoice");

var total = evaluator.EvaluateCell(
    sheet,
    row: 6,
    col: 4);

Console.WriteLine(total);

Output:

318.6

11. Professional workbook styling

FormulaEngineer produces workbooks that are ready to open, present, and share—not raw grids requiring manual formatting.

using FormulaEngineer.Api;
using FormulaEngineer.Api.Styling;

var headerStyle =
    ExcelStyle.Default.With(
        font: ExcelFontStyle.Default.With(
            bold: true,
            color: ExcelColor.FromRgb(255, 255, 255)),
        fill: ExcelFillStyle.Solid(
            ExcelColor.FromRgb(31, 78, 121)),
        alignment: ExcelAlignmentStyle.Default.With(
            horizontal:
                ExcelHorizontalAlignment.Center));

var currencyStyle =
    ExcelStyle.Default.With(
        numberFormat:
            ExcelNumberFormatStyle.Custom("$#,##0.00"));

using (var writer =
       new ExcelStyledWriter("sales-report.xlsx"))
{
    using (var sheet =
           writer.CreateWorksheet("Sales"))
    {
        sheet.WriteRow(
            new object?[]
            {
                "Product",
                "Units",
                "Revenue"
            },
            headerStyle);

        sheet.WriteRow(
            new object?[]
            {
                "Formula Engine",
                12,
                5988m
            },
            new ExcelStyle?[]
            {
                null,
                null,
                currencyStyle
            });

        sheet.WriteRow(
            new object?[]
            {
                "Streaming Writer",
                8,
                2204m
            },
            new ExcelStyle?[]
            {
                null,
                null,
                currencyStyle
            });
    }

    writer.Close();
}

Styling and presentation capabilities

Capability	Examples
Fonts	Family, size, bold, italic, underline, and color
Fills	Solid colors and theme-based fills
Borders	Per-side styles, colors, and combinations
Number formats	Currency, percentage, date, time, accounting, and custom formats
Alignment	Horizontal, vertical, indentation, rotation, and wrapping
Layout	Column widths, row heights, merged cells, and auto-fit
Conditional formatting	Data bars, color scales, icon sets, and formula rules
Rich text	Multiple formatted runs inside one cell
Tables	Real Excel tables with styles and structured references
Notes and comments	Traditional notes and threaded comments
Images and shapes	Embedded images and worksheet drawing objects
Charts	Workbook charts anchored to worksheet cells
Sparklines	Compact in-cell trend visualizations
Dashboards	KPIs, summary tables, charts, and conditional formatting

Explore the styling examples →

12. Streaming workbook processing

FormulaEngineer is designed for both compact business reports and high-volume data exports.

Its streaming reader and writer provide:

Forward-only workbook processing
Single-enumeration access
Predictable memory usage
A flat memory profile regardless of workbook size
No dependency on an installed Excel application
Styling and layout during workbook generation
Server-friendly processing for APIs and background jobs

Use FormulaEngineer for:

Financial reports
Invoice generation
Operational exports
Uploaded workbook processing
Formula-driven business rules
Automated workbook validation
Background recalculation jobs
Large server-side XLSX exports
Executive dashboards
CI/CD workbook testing

13. More than formula evaluation

Formula evaluation is FormulaEngineer's defining capability—but it is not the only one.

Area	Capabilities
Core styling	Fonts, fills, borders, number formats, alignment, and protection
Layout and auto-fit	Column widths, row heights, merged cells, wrapped text, and streaming auto-fit
Conditional formatting	Data bars, color scales, icon sets, and formula-driven rules
Rich text	Multiple fonts, colors, and styles within one cell
Tables	Real Excel tables with styles and structured references
Notes and comments	Traditional notes and threaded comments
Images	Embedded PNG and JPEG images
Shapes	Worksheet drawing objects
Charts	Professional charts connected to workbook data
Sparklines	Line, column, and win/loss sparklines
Dashboards	Attractive, formula-driven business dashboards

Advanced capabilities are opt-in so applications only enable the workbook features they need.

14. Deployment

FormulaEngineer can run anywhere compatible .NET applications run.

Supported application types

ASP.NET Core applications
REST APIs
Background services
Console applications
Windows services
Linux services
Docker containers
CI/CD pipelines
Azure Functions
AWS Lambda
Blazor applications
WinForms applications
WPF applications

No Excel installation, desktop session, Office process, or COM automation is required.

15. Examples and resources

Resource	Description
Formula examples	Create, read, and recalculate workbook formulas
Styling examples	Build professionally formatted workbooks
CI/CD examples	Use FormulaEngineer in automated environments
Supported functions	Browse all 461 supported Excel functions
Formula validation	Review real-workbook validation scenarios
Live demo	Try formula evaluation in the browser
NuGet package	Install the latest FormulaEngineer release
Pricing	Review trial, solo, and team licence options

16. Licensing

FormulaEngineer is commercial software with a built-in 30-day free trial.

Free trial

Full access to FormulaEngineer features
No licence activation required
Starts automatically on first use
No credit card required
Available on Windows, Linux, and macOS
Intended for evaluation and testing

Paid licences

Paid solo and team licences include commercial use, updates, bug fixes, and support according to the selected plan.

Activate a paid .lic file before using the workbook APIs:

using FormulaEngineer.Licensing;

LicenseManager.ActivateFromFile("license.lic");

View current pricing and licence options →

Read the policies and licensing terms →

FormulaEngineer is licensed software, not open-source software. Access to this repository, its documentation, or its examples does not grant a licence to the proprietary FormulaEngineer package.

17. Contact

Need a function that is not yet supported? Want to check whether FormulaEngineer can process a specific workbook?

Send the function name, formula example, and a minimal sanitized workbook when possible.

Email: nasrullahkazmi@nasvelocityexcel.com
Contact: nasvelocityexcel.com/contact
Website: nasvelocityexcel.com
NuGet: FormulaEngineer

Recalculate workbook logic. Generate polished Excel output. Keep Excel off the server.

FormulaEngineer — the complete .NET Excel solution.

Install from NuGet · Try the live demo · Explore examples

Name		Name	Last commit message	Last commit date
LICENSE.txt		LICENSE.txt
README.md		README.md

Navigation Menu

Repository files navigation

FormulaEngineer

1. Introduction

Why recalculation matters

2. Why FormulaEngineer?

Real formula evaluation

461 Excel-compatible functions

Excel-style workbook behavior

High-performance streaming I/O

Complete workbook presentation

Cross-platform and server-ready

3. Key capabilities

4. Package summary

5. Function coverage

Popular supported functions

6. Excel-style formula behavior

7. Validation

Representative validation scenarios

Test formula recalculation fairly

8. Installation

9. Quick start

Create a workbook containing a formula

Open the workbook and evaluate the formula

10. Real-world invoice example

11. Professional workbook styling

Styling and presentation capabilities

12. Streaming workbook processing

13. More than formula evaluation

14. Deployment

Supported application types

15. Examples and resources

16. Licensing

Free trial

Paid licences

17. Contact

Recalculate workbook logic. Generate polished Excel output. Keep Excel off the server.

About

Releases

Contributors

Latest commit

History

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Repository files navigation

FormulaEngineer

1. Introduction

Why recalculation matters

2. Why FormulaEngineer?

Real formula evaluation

461 Excel-compatible functions

Excel-style workbook behavior

High-performance streaming I/O

Complete workbook presentation

Cross-platform and server-ready

3. Key capabilities

4. Package summary

5. Function coverage

Popular supported functions

6. Excel-style formula behavior

7. Validation

Representative validation scenarios

Test formula recalculation fairly

8. Installation

9. Quick start

Create a workbook containing a formula

Open the workbook and evaluate the formula

10. Real-world invoice example

11. Professional workbook styling

Styling and presentation capabilities

12. Streaming workbook processing

13. More than formula evaluation

14. Deployment

Supported application types

15. Examples and resources

16. Licensing

Free trial

Paid licences

17. Contact

Recalculate workbook logic. Generate polished Excel output. Keep Excel off the server.

About

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Resources

Stars

Watchers

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Contributors