How to Calculate Percentages in Excel (Every Formula)

Percentage of a total

What percentage is part X of total Y?

=part / total
=B2 / $B$10    (B2 is the part, B10 is the grand total)
-- Format the result cell as percentage (Ctrl+Shift+5)

Percentage change

How much did something grow or shrink?

=(new_value - old_value) / old_value
=(C2 - B2) / B2
-- Positive = growth, negative = decline
-- Format as percentage

Add a percentage to a value (e.g. VAT)

=value * (1 + percentage)
=B2 * 1.20    (add 20% VAT)
=B2 * 1.15    (add 15%)
-- The 1 keeps the original, the 0.20 adds the percentage

Subtract a percentage (e.g. discount)

=value * (1 - percentage)
=B2 * 0.80    (apply a 20% discount — keeps 80% of original)
=B2 * (1 - C2)  (C2 contains the discount rate)

What percentage of target has been achieved?

=actual / target
=C2 / B2
-- Format as percentage. Over 100% = target exceeded

Work backwards — find the original value before a percentage was added

=value_after / (1 + percentage)
=B2 / 1.20    (find the pre-VAT price from a VAT-inclusive price)

💡 Format as percentage, don't multiply by 100

When you write a percentage formula, the result is a decimal (0.25 means 25%). Apply percentage formatting (Ctrl+Shift+5) and Excel displays it as 25% automatically. Don't multiply by 100 — that gives you 25 which can't be used as a percentage in further calculations.

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How to calculate percentagesin Excel