Calculate a percent increase from A to B

Subtract the start from the new value, divide by the absolute value of the start, multiply by 100. If the new value is lower, this page refuses the pair — use percent decrease. A start of zero cannot be a base.

hausse = (arrivée − départ) ÷ |départ| × 100

The engine’s increase mode requires a nonnegative gap. You see the percent rise, the raw difference, and both endpoints. No annualizing: 25% from one month to the next is not a yearly rate. Successive percents do not cancel (see FAQs).

Starting value

The old value, used as the denominator. A smaller start makes the same raw rise look like a larger percent.

New value

The new value. It must be ≥ the start. For a drop, open the percent-decrease calculator.

Assumptions

• Both numbers describe the same quantity, before then after.
• The comparison base is the start, not the new value and not the midpoint.

Limits

• A 100% increase doubles; a 200% increase triples. Everyday speech often confuses “twice as much” with “+200%.”
• No compounding and no CAGR: one period only.

Read the result as “relative to what it was.” 80 to 100 is +25% on 80, not +20% on 100. If you are comparing two quotes with no timeline, the symmetric gap on the percent-difference page is often the fairer reading.

• Dividing the gap by the new value (20/100) instead of the start (20/80).

  A relative increase is always from the original base, here 80.

• Expecting +25% then −25% to return to 80.

  After +25% you are at 100. −25% of 100 is 25, leaving 75, not 80. Sequential percents do not undo each other.

• PercentageEnter two numbers of the same kind. The tool returns (part ÷ total) × 100 — useful for a test score, a slice of a budget, or a share of a count.
• 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.
• CAGRCAGR is the fictional constant annual rate that would take a starting value to an ending value in n years. It smooths the trip: a crash and a rebound disappear into one number.

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.