Two questions that sound alike
“Increase 80 by 15%” gives you the rate and asks for a new amount. “Find the increase from 80 to 92” gives you both amounts and asks for a rate. Identify which value is missing before selecting a tool.
The dedicated increase and decrease comparison tools take before-and-after values. To apply a known rate, use the basic calculator with the multiplier formula shown here.
Apply and reverse a change
An increase of r% uses 1 + r/100; a decrease uses 1 − r/100. The initial 1 preserves the original amount, while the extra part adds or removes the change.
To recover an original amount, divide the final value by its multiplier. Subtracting the same percentage from the final value does not reverse an increase because the base has changed.
Successive changes multiply
A 20% discount followed by a further 10% discount uses 0.8 × 0.9 = 0.72. The combined discount is 28%, not 30%. Order does not change this result when the factors apply to the same running amount.
A 100% decrease produces zero. A larger decrease produces a negative mathematical result, which may not make sense for a price or a physical quantity.
LET’S WORK IT THROUGH
A price of 80 increases by 15%. What is the new price?
- 15% = 0.15.
- The growth factor is 1 + 0.15 = 1.15.
- 80 × 1.15 = 92.
THE ANSWERThe new price is 92. Dividing 92 by 1.15 recovers 80.
YOUR TURN
A small check for understanding.
A price of 240 is reduced by 25%. What remains?
Reveal the answer
180. Multiply 240 by 0.75.
Now try your own numbers.
The percentage increase includes input guidance and the limits of its supported calculations. Use it alongside the method above.
Open Percentage increase ↗A note on precision: preserve exact fractions where possible and round numerical results at the end. Found an unclear step? Prepare a correction report.