Free percentage calculator

Switch calculation mode, enter two numbers, and see the result instantly. All math stays in this tab — no server upload.

Pick a mode below. Percent fields accept negatives and decimals (e.g. −10% change or 12.5% of a price).

Percent (%)Of (number)

20% of 150 = 30

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How to use this tool

1
Open percentage calculator
Choose a mode: % of, what %, change, increase, or decrease.
2
Enter values
Type the two numbers for your scenario.
3
Read the result
Use the highlighted line for the answer or copy the number.

Runs locally?	Yes — arithmetic runs in your browser.
Is anything uploaded?	No. Numbers never leave this tab.
Negative percent?	Allowed — useful for discounts or losses in % change mode.
vs discount math?	Use Decrease for “price −20%”; use % change to compare before/after totals.

Find X% of a number, what percent one value is of another, percent change, and increase/decrease — runs locally.
Runs locally?: Yes — arithmetic runs in your browser.
Is anything uploaded?: No. Numbers never leave this tab.
Negative percent?: Allowed — useful for discounts or losses in % change mode.
vs discount math?: Use Decrease for “price −20%”; use % change to compare before/after totals.

How is “% of” calculated?▾

Multiply the base by (percent ÷ 100). Example: 20% of 150 = 30.

What is percent change?▾

((new − original) ÷ original) × 100. A drop from 200 to 150 is −25%.

Increase vs % of?▾

Increase adds a percent to the value (80 + 10% → 88). % of returns only the portion (10% of 80 → 8).

Decimals?▾

Yes — prices, grades, and rates with fractional percents are supported.

Why “cannot divide by zero”?▾

“What %” needs a non-zero whole; % change needs a non-zero original.

Offline?▾

Works offline after the page loads.