How to Calculate Percentage in Excel
Calculate percentages in Excel for budgets, margins, growth, discounts, and completion rates with practical formulas that avoid common mistakes.
Reviewed by Griddy
Updated for current Excel and Google Sheets workflows, with examples chosen to map back to real spreadsheet tasks rather than abstract formula syntax.
Percentages in Excel are just division with percentage formatting. The hard part is choosing the right numerator and denominator.
Use percentages for budget share, margin, growth, discount rates, completion rates, and anything else where the question is "what part of the whole is this?"
Basic percentage formula
=part/totalIf B2 is the amount spent and C2 is the total budget, the percentage used is:
=B2/C2Format the result as Percentage. If the answer is 0.42, percentage formatting displays it as 42%.
⚠ WATCH OUT
42% into 4200%.Example: budget percentage used
Suppose a marketing budget has:
- planned budget in
B2 - actual spend in
C2
To calculate how much of the budget has been used:
=C2/B2If the planned budget is $5,000 and actual spend is $3,750, the formula returns 75% after percentage formatting.
That percentage is often more useful than the raw amount because it shows how much room is left before the category is over plan.
Percent change formula
Use percent change when you want to compare a new value against an old value:
=(new_value-old_value)/old_valueIf last month revenue is in B2 and this month revenue is in C2:
=(C2-B2)/B2A positive result means growth. A negative result means decline.
Margin percentage
Margin is profit divided by revenue:
=(revenue-cost)/revenueIf revenue is in B2 and cost is in C2:
=(B2-C2)/B2This is different from markup. Margin uses revenue as the denominator. Markup uses cost as the denominator.
Increase or decrease a value by a percentage
To increase a price by a percentage:
=B2*(1+C2)If B2 is $100 and C2 is 15%, the result is $115.
To decrease a price by a percentage:
=B2*(1-C2)If C2 is 20%, the result is $80.
Common percentage mistakes
| Mistake | What happens | Fix |
|---|---|---|
| Dividing by the wrong base | Percentage tells the wrong story | Decide what the "whole" is before writing the formula |
| Multiplying by 100 twice | Result shows as thousands of percent | Use division, then apply Percentage format |
| Mixing margin and markup | Pricing math gets distorted | Use revenue for margin, cost for markup |
| Dividing by zero | Excel returns #DIV/0! | Use IFERROR or check that the base is not zero |
The Griddy way
Percentage formulas are simple until a sheet mixes budget usage, margin, discounts, and growth in the same model.
"Add percent-used, percent-change, and gross-margin columns to this budget sheet"
Griddy can choose the right formula for each column and format the results as readable percentages.
Skip the manual work
Describe it. Griddy does it.
Instead of writing this formula yourself, just tell Griddy what you need in plain English. Works in Excel and Google Sheets.