= Write My Formula

Excel data validation formula helper

Write the Excel data validation formula for your rule.

Describe what Excel should allow in the cell, include the first cell in the validation range, and get a custom TRUE/FALSE formula with copy checks before you apply it.

Request

Formula request

2 guest tries left
Mode
Spreadsheet
Upgrade $9

Purpose-built inputs

A focused workflow for everyday spreadsheet work.

Structured formula builder

Task, table context, target range, and function hint keep the request specific.

Write / Explain / Fix modes

Generate a new formula, translate a pasted one, or diagnose common syntax issues.

Excel and Sheets toggle

Compatibility notes call out modern functions and platform-specific behavior.

Formula-bar output

The result is formatted for scanning and placed next to a copy button.

Common formulas

Pick the formula you came for.

Excel formula help

Get help writing, explaining, or fixing one Excel formula with range notes and checks before you paste.

AI Excel formula generator

Generate an Excel formula from plain English with range notes, an explanation, and checks before you paste.

Formula Bot alternative

Use a focused formula workbench when you need a formula, explanation, or fix instead of a full spreadsheet-analysis suite.

SheetSolver AI alternative

Compare a narrow formula helper for writing, explaining, and fixing formulas against broader spreadsheet AI suites.

Percentage formulas

Build percent of total, percent change, discount, markup, tax, tip, and completion-rate formulas.

Fix my Excel formula

Paste a broken formula and get a corrected version with checks for errors, text cells, ranges, and fallbacks.

Excel formulas not working

Fix formulas that stop calculating after imports, copied ranges, locale settings, or text-number mismatches.

Excel #VALUE! error

Repair formulas blocked by text values, hidden spaces, wrong argument types, dates, or subtraction syntax.

Excel #NAME? error

Fix formulas with misspelled functions, undefined names, missing quotes, or unsupported functions.

Excel #DIV/0! error

Fix formulas blocked by zero or blank denominators, ratio logic, averages, and IFERROR tradeoffs.

Excel circular reference

Fix formulas that point back at their own result cell or need deliberate iterative-calculation checks.

Excel #REF! error

Repair formulas broken by deleted rows, moved cells, invalid references, or shifted lookup ranges.

VLOOKUP #N/A error

Fix lookup formulas that return #N/A because of exact-match settings, text-number mismatches, or range setup.

Date formulas

Create due dates, workday counts, month-end dates, date differences, and overdue checks.

FILTER formulas

Return matching rows for status, region, date, text, and threshold conditions.

Text formulas

Split, extract, join, trim, clean, and replace text from messy imported cells.

Data validation formulas

Block bad IDs, duplicate values, missing fields, and invalid entries with custom TRUE/FALSE rules.

XLOOKUP formulas

Return matching values with separate lookup and return ranges.

INDEX MATCH formulas

Build flexible lookup formulas for left lookups, two-way lookups, and older Excel files.

SUMIFS formulas

Total rows that match status, date, category, customer, or region rules.

Use case

Excel data validation formula helper for spreadsheet work.

Help Excel users turn entry rules into custom data-validation formulas that return TRUE for allowed values and FALSE for values Excel should reject.

What this page gives you

  • A custom validation formula for the entry rule you describe.
  • A plain-English read of why the formula returns TRUE for accepted entries.
  • Checks for first-cell references, fixed ranges, blanks, duplicate handling, and valid/invalid test entries.

When to use it

Use this page when Excel Data Validation is set to Allow: Custom and you need a formula for allowed entries, such as a required ID prefix, unique values, valid email-style text, a date window, or a required field. It is strongest when you know the first cell in the range where the rule will be applied.

Do not use a validation formula as a whole-workbook audit. Data validation helps block future entries; it does not prove every existing row is clean, and users can still paste or import data in ways that need a separate review.

Worked example

For customer IDs in A2:A500, a validation rule can require the ID- prefix and reject duplicates in the applied range.

=AND(LEFT(A2,3)="ID-",COUNTIF($A$2:$A$500,A2)=1)

The formula returns TRUE only when A2 starts with ID- and the same value appears once in the validation range. A2 stays relative so Excel can evaluate each row, while the COUNTIF range stays fixed.

Check before you paste

  • Custom data-validation formulas should return TRUE for allowed entries and FALSE for entries Excel should reject.
  • Use dollar signs only where the reference must stay fixed as the validation rule is applied down the range.
  • Decide whether blanks should be accepted before adding ISBLANK or LEN checks.
  • Test one valid value and one invalid value in Excel after applying the rule.

Upgrade when the work piles up

Keep going when the sheet gets complicated.

Try twice as a guest. Free accounts get 3 runs per week plus a monthly product email. Upgrade when formula work becomes a recurring part of the week.

Founding access

$9

500 formula runs per month in this browser, early access pricing, and account access as it ships. Stripe redirects you back after payment.

Upgrade with Stripe