Excel Library for .NET — Read, Recalculate & Style .xlsx

Styled output

Not just calculation. Presentation.

FormulaEngineer writes the workbook a person will actually open — fonts, fills, number formats, merged banners, conditional formatting, tables and charts — in the same streaming pass that computes the numbers.

An Excel dashboard generated by FormulaEngineer, showing a KPI band with total revenue, costs and gross margin, above a performance table with data bars and colour-coded target status.

Generated in C#. No Excel, no COM, no template file.

Get on NuGet Styling examples Download .xlsx

29 live formulas 18 format rules 13.7 KB file

Generated in C#. No Excel, no COM, no template file.

FormulaEngineer for .NET

Evaluate Excel formulas in C# without Excel or COM interop

FormulaEngineer reads, writes, and recalculates Excel (.xlsx) files directly inside .NET applications. Use it when workbooks are generated, uploaded, modified, or recalculated on a server without opening Excel.

Get on NuGet View supported functions

No Excel installed No COM automation Server-side .NET

Program.cs

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);

Calculate workbook logic in pure managed .NET.

Why formula evaluation matters

Reading cached values is not the same as recalculating formulas

An .xlsx file may contain formula results saved by Excel earlier — but there is no guarantee a cached value is present at all. Even when it is, it can be missing, stale, or wrong after inputs change in code. FormulaEngineer focuses on recalculating the workbook logic, not just reading old saved results.

See what it does View pricing

Useful for uploaded files, generated reports, APIs, and background jobs

Cached value from file

Old result

After input change

Formula must be recalculated

FormulaEngineer

New calculated result

Built for Excel-style behavior

References, ranges, errors, lookups, dates, text, and more

Formula evaluation is more than parsing strings. FormulaEngineer handles workbook references, range behavior, Excel-style errors, type coercion, lookup functions, date functions, text functions, and circular reference detection.

Explore supported functions Start free trial

Supports 430+ Excel functions and growing

SUMIFS XLOOKUP VLOOKUP INDEX MATCH WORKDAY DATE TEXT IFERROR COUNTIFS HLOOKUP DAYS360

Read, write & recalculate

Open existing workbooks, create new ones, and evaluate formulas instead of relying on cached .xlsx values.

Excel-style behavior

Handles ranges, references, coercion, errors, and circular references.

Server-side ready

Designed for ASP.NET, APIs, Linux, containers, and background jobs.

Full cell styling

Fonts, fills, borders, number formats, alignment, merged cells, and column layout.

Conditional formatting

Data bars, colour scales, icon sets, and formula rules that Excel evaluates when the file opens.

Tables, charts & notes

Real Excel tables, charts, sparklines, images, and threaded comments — all opt-in.

A pricing dependency map: revenue, discount, net revenue and tax feeding a formula graph that resolves to a final calculated price.

Four dependencies resolved into one price

Spreadsheets carry real business logic. Run it inside your .NET application.

Pricing rules, financial models, forecasts, and operational logic live in Excel formulas — often as a chain of dependent cells nobody wants to rewrite in C#.

FormulaEngineer resolves those dependencies and recalculates the result in pure managed .NET. No Excel install, no COM interop, no template file.

A cached value is a guess. Recalculate and know.

Every read parses the formula, resolves its references, evaluates the values, and formats the result — rather than trusting whatever Excel happened to save last time the file was opened.

Ranges, coercion, Excel-style errors, and circular reference detection are all handled, across 430+ functions.

Numbers alone are not a report. Ship a workbook people can read.

ExcelStyledWriter applies fonts, fills, borders, number formats, alignment, merged banners, column widths, and row heights as the rows stream out. Only the current row is held in memory, so the same code path handles a ten-row summary and a multi-million-row export.

29 live formulas 18 format rules 25 merged ranges 36 styles from 9 fonts 13.7 KB file

Download this workbook

Formatting that reacts to the data. Not colours frozen at export time.

Data bars, colour scales, icon sets, and formula-driven rules are written as real conditional formatting, so Excel re-evaluates them when the numbers change.

Excel tables, charts, sparklines, images, shapes, and threaded comments are all available, each behind its own opt-in flag so unused features cost nothing.

Machine hash calculator

Generate the unique hash needed for your FormulaEngineer license.

How to find your hardware identifiers

1
Open PowerShell as your normal user (no admin needed).

CPU ID

Get-CimInstance Win32_Processor | Select-Object -ExpandProperty ProcessorId

Motherboard serial

Get-CimInstance Win32_BaseBoard | Select-Object -ExpandProperty SerialNumber

4
System drive volume serial
```
cmd /c vol C:
```

1
Open a terminal as your normal user. Some commands may need sudo.
2
CPU ID (machine ID)
```
cat /etc/machine-id
```
3
Motherboard serial
```
sudo cat /sys/class/dmi/id/board_serial
```
4
Root volume UUID
```
findmnt -n -o UUID /
```

1
Open Terminal (Applications → Utilities → Terminal).

Platform UUID (enter in the CPU ID field)

ioreg -rd1 -c IOPlatformExpertDevice | awk -F'"' '/IOPlatformUUID/ { print $(NF-1); }'

3
Motherboard serial — macOS doesn't expose one. Leave that field blank.

Volume UUID

diskutil info / | awk -F': *' '/Volume UUID/ { print $2; }'

Enter your values (all fields required)

Windows

FormulaEngineer — a .NET library to create, read, recalculate and style Excel (.xlsx) files in C# without Excel or COM interop

Not just calculation. Presentation.

Evaluate Excel formulas in C# without Excel or COM interop

Reading cached values is not the same as recalculating formulas

References, ranges, errors, lookups, dates, text, and more

01 Spreadsheets carry real business logic

02 From workbook inputs to a live result

03 Generate styled workbooks, not raw grids

04 Conditional formatting, tables, and charts

Machine hash calculator

How to find your hardware identifiers

Enter your values (all fields required)