Percentage calculator

Client

Three common patterns—pick a mode, enter numbers, and read the result. Nothing leaves your tab.

X% of Y: percentage of a value. X is what % of Y: part-to-whole. % change: from an old value to a new value.

Percent (X)

Of (Y)

Result: 12

Common use cases

Find what percent one value is of another for reporting and quick ratio checks.
Compute percent change between two measurements for growth or regression summaries.
Take a percentage of a base amount for discounts, tips, or tax estimates before rounding rules.

Mixing up “percent of” and “percent change”
Part-to-whole uses different math than old-to-new change—pick the mode that matches your question.
Rounding too early in multi-step chains
Keep extra precision internally, then round once for display to avoid drift.

Are calculations done on your servers?

No. All math runs locally in your browser tab.

Is this financial or tax advice?

No. It is a generic calculator—confirm rates and rounding with authoritative sources.

Related utilities you can open in another tab—mostly client-side.