Percentage calculator
Compute a discount, VAT, margin, share or evolution in real time. Fill in any two boxes, the third adjusts automatically. Bi-directional, with full formula and multiplier coefficient so you actually understand the math.
Go deeper
Three calculations, one interface
90% of everyday percentage problems fall into three categories: applying a percentage (variation), finding a share (proportion), or measuring an evolution between two values. This calculator covers all three, with a twist: every field is editable, not just the "result". Change any box and the others recompute.
VAT & net/gross price
Enter 100 net and 20%, you get 120 gross. Enter 120 gross and 20%, you recover 100 net. Same field, two calculation directions.
Discounts & sales
"-30% on a $79 item" → $55.30. You can also recover the original price from the sale price.
Evolution & margin
From 80 to 100 = +25%. Track revenue, grade, stock or weight progress.
The 3 formulas to remember
The multiplier coefficient — your pro shortcut
A 20% increase = × 1.2. A 30% decrease = × 0.7. Learning these coefficients lets you compute any variation in your head. The tool displays it under every result to help you internalize it.
FAQ
How do I calculate a gross price from a net price?
"Variation" tab, tick "Add (VAT, Margin)", enter your net price in field 1 and the VAT rate (20%, 10%, 5.5%...) in field 2. The gross price appears in field 3. You can also do the reverse: enter the gross and the rate, the tool gives you the net.
How do I recover the price before a discount?
"Variation" tab, tick "Discount (Sales)", enter the discounted price in field 3 and the discount percentage in field 2. Field 1 shows the original price.
What's the difference between "variation" and "evolution"?
Variation applies a known percentage to a value (e.g. +20% on 100). Evolution measures the percentage between two given values (e.g. from 80 to 100 = +25%). It's the same math taken from the other angle.
What is the multiplier coefficient?
It's the number you directly multiply the initial value by to get the final value. +20% = × 1.2; −30% = × 0.7. It skips the full formula and speeds up mental math.
Are my values saved?
No. Everything is calculated live in your browser, no data is sent or stored. You can close the page with peace of mind.
