Percentage Increase/Decrease Calculator
🔒 In your browserPercentage increase or decrease between two values.
How it works
Find the percentage increase or decrease between two numbers — an old price and a new one, last year's marks and this year's, or any before-and-after pair.
🔒 Calculated entirely in your browser — nothing is uploaded.
🔒 Calculated in your browser: your marks, grades and dates are never uploaded. Grading rules and conversion formulas vary by board and university, so treat the result as a reliable estimate and confirm anything official with your institution.
About the Percentage Increase/Decrease Calculator
This free percentage change calculator finds the increase or decrease between two numbers — an old price and a new one, last term's marks and this term's, or any before-and-after pair. Enter the original and new values for an instant answer.
It runs in your browser and clearly labels whether the change is an increase or a decrease.
How percentage change works
Percentage change is the difference between the two values divided by the original, times 100. Going from 80 to 100 is a 25% increase (a rise of 20 over the original 80); going from 100 to 75 is a 25% decrease. The original value is always the reference point, which is why the same absolute change gives a different percentage depending on where you started.
Why an increase and decrease don't cancel out
A 25% rise followed by a 25% fall does not return you to the start, because each percentage is taken from a different base. Start at 100, add 25% to reach 125, then take 25% off 125 (which is 31.25) and you land at 93.75 — not 100. This is why price rises and later 'discounts' of the same percentage rarely undo each other, and why the order and base matter when you read percentage changes.
Frequently asked questions
How do I calculate percentage increase?
Subtract the old value from the new, divide by the old value, and multiply by 100. From 80 to 100: (100 − 80) ÷ 80 × 100 = 25% increase.
How is percentage decrease different?
It's the same formula; the result is simply negative when the new value is lower. From 100 to 75 is a 25% decrease.
Does a 20% rise then a 20% fall return the original?
No. The fall is taken from the higher value, so you end up below where you started — 100 becomes 120, then 96. Equal percentages up and down don't cancel because their bases differ.
Why can't the original value be zero?
Percentage change divides by the original value, and dividing by zero is undefined — there's no meaningful percentage rise from nothing.
Is this the same as percentage points?
No. Going from 40% to 50% is a rise of 10 percentage points but a 25% increase. This tool reports the percentage change; percentage points are just the raw difference.
Is my data private?
Yes — everything is calculated in your browser.