Percentage calculator – what percentage is it?
Enter the numbers to see the result and three ways to reach it – the way it is done in the Polish exam after grade 8.
Three methods, one result
Squares: the whole number is 100 squares, which is 100%. The shaded squares show the result as a percentage.
How do you work out what percentage a number is?
A percentage (procent) is one hundredth. To find what percentage a part is of a whole, divide the part by the whole and multiply by 100%. Example: what percentage is 27 out of 30?
27 : 30 = 0,9 → 0,9 · 100% = 90%
The second method starts with 1% of the whole. 1% of 30 is 0,3, and 27 : 0,3 = 90, so the answer is 90%.
Polish schools and the exam write division with a colon (:), multiplication with a raised dot (·) and decimals with a comma: 0,9. In the calculator fields you can type either a comma or a point.
How do you find a percentage of a number?
Work out 1% (divide by 100) and multiply by the number of percent. Example: 20% of 150.
150 : 100 = 1,5 → 20 · 1,5 = 30
Or turn the percentage into a decimal (ułamek dziesiętny): 20% = 0,2, and 0,2 · 150 = 30.
By what percentage has a number gone up or down?
Divide the difference by the number you started with. From 80 to 100 the difference is 20, and 20 : 80 = 0,25, so it is 25% more.
The other way round, from 100 to 80, the difference is also 20, but 20 : 100 = 0,2, so it is 20% less. That is why “by what percentage more” and “by what percentage less” give two different answers.
How do you find the price before a discount?
After a 25% discount, 75% of the price is left. If a hoodie now costs 90, then 90 is 75% of the old price.
90 : 75 = 1,2 (that is 1%) → 1,2 · 100 = 120
The most common mistake: 90 + 25% of 90 = 112,5. That is wrong, because the discount was taken from the old price, not from 90.
Why do percentages matter in the Polish exam?
Polish pupils study percentages in grades 4–8 of primary school (szkoła podstawowa), and the exam at the end of grade 8 (egzamin ósmoklasisty) includes percentage problems. In 2025, question 1 tested percentage calculations based on data from a chart – 59% of pupils earned the point (CKE report 2025, in Polish). The most common error (about 38% of pupils) was to take the difference between two amounts as the percentage by which one is larger than the other.
Source of the requirements: podstawa programowa, the national curriculum, Dz.U. 2024 poz. 996.
What else might be useful?
Glossary: English – Polish
- percentage, percent – procent
- part – część
- whole – całość
- difference – różnica
- discount – obniżka
- price increase – podwyżka
- proportion – proporcja
- decimal – ułamek dziesiętny
The calculator works in your browser and sends nothing. Results that cannot be written exactly are rounded (sign ≈) to 2 decimal places. Enter non-negative numbers with at most 4 decimal places (12,5 and 12.5 both work). Spotted a mistake? Write to: kontakt@mamwynik.pl.