Find what percent a part is of a whole

Both inputs are read as decimals. The engine divides the part by the total, multiplies by 100, and rounds the display. Internal precision is higher than what you see. No unit conversion happens: $25 of $200 and 25 students of 200 students both yield 12.5%.

p = (part ÷ total) × 100

This page answers only “what fraction of the total, on a base of 100?” It does not measure a change over time. If the total is 0, division is undefined and the run stops. JavaScript floating point is not banker’s decimal arithmetic; display rounding is typically two places.

Part

Numerator of the ratio. It may exceed the total (a budget at 120%, for example).

Total

Denominator: the 100% reference. Zero is refused. The sign of the total carries into the result.

Assumptions

• Part and total use the same unit.
• You want part relative to total, not a percent change from one date to another.

Limits

• Display rounding hides extra floating-point digits.
• Increase, decrease, discount, and tip each have their own page.

12.5% means 12.5 hundredths of the total — one eighth. If your two numbers are “before” and “after,” use percent increase or percent decrease instead.

• Swapping part and total (200 of 25 instead of 25 of 200).

  The part is what you measured; the total is the reference. Here that is 25 / 200.

• Mixing up “25% of 200” with “25 is what percent of 200.”

  25% of 200 is 50. This page does the other direction: 25 is 12.5% of 200.

• Percent increaseGive a starting amount and a higher later amount. The tool reports the rise relative to the start, not a “neutral” gap between two figures.
• Percent decreaseEnter an original amount and a smaller later amount. The result is the drop relative to the original — the same idea as a markdown, without applying a sale price formula.
• Percent differenceA and B are not labeled “before” and “after.” You get the absolute gap, the gap relative to A, relative to B, and the symmetric gap (divided by the average). That is not a percent increase.
• RatioTwo integers in, a reduced ratio out (8 : 12 becomes 2 : 3), plus the quotient A/B and each term’s weight in the sum of absolute values — not “A as a percent of B.”
• DiscountApply one markdown: the original times (1 − p/100). Stacked percents off are not a sum: 20% then 20% leaves 64% of list, a 36% combined cut, not 40%.

Written by Rédaction HexaCalc (editorial team). Content last updated: August 25, 2026. No third-party medical or financial review is claimed.

This calculation uses a standard mathematical identity. See also the methodology.