vmbo havo vwo
Percentage calculator
Calculator
Pick the mode, enter the numbers (a comma or a point is fine) and read the steps under the answer.
Quick answer
A percent of a number: number × percent ÷ 100. 15% of 80 is 80 × 15 ÷ 100 = 12.
Part of a whole: part ÷ whole × 100. 12 out of 80 is 15%.
Change: (new − old) ÷ old × 100.
What is a percentage?
Percent means per hundred. 25% is 25 per 100, the fraction 25/100, or the decimal 0.25. That lets you compare groups of different sizes: 40 out of 160 and 25 out of 100 are both 25%.
Three directions keep coming back. From percent to amount: number × percent ÷ 100. From part to percent: part ÷ whole × 100. The reverse, when you need the whole: part ÷ percent × 100 (for example: 21 is 30% of what?).
Do not use percent change when the starting value is 0: you cannot divide by zero. And do not swap part and whole: 12 out of 80 is not the same as 80 out of 12.
In Dutch secondary school (vmbo, havo and vwo — the three main tracks), percentages return in ratios, statistics, exponential growth and (on havo/vwo) growth factors. The official programs are on Examenblad.nl.
Examples by level
The tabs use the Dutch school names once: vmbo is the more practical track, havo sits in the middle, vwo is the university-preparatory track. The same formulas apply; the wording gets denser.
15 of 25 students finished their homework. What percent is that?
- Part and wholepart = 15, whole = 25
- Divide15 ÷ 25 = 0.6
- Times 1000.6 × 100 = 60%
60% of the class finished the homework.
A shop had 240 customers and now has 192. What percent remain, and what percent left?
- Percent still there192 ÷ 240 = 0.8 → 80%
- Complement100% − 80% = 20% left
- Check via change((192 − 240) ÷ 240) × 100 = −20%
That is a 20% decrease. The growth factor from 240 to 192 is 192 ÷ 240 = 0.80.
A laptop costs €899 excluding 21% BTW (Dutch value-added tax, VAT). What is the price including BTW?
- BTW amount899 × 0.21 = 188.79
- Add899 + 188.79 = 1,087.79
- One factor899 × 1.21 = 1,087.79
The price including BTW is €1,087.79. The standard rate 21% and the reduced rate 9% are published by the Belastingdienst (Dutch tax authority); those figures can change by year.
Common mistakes
Wrong
25% of 80 as 80 ÷ 25 = 3.2
Right
25% = 0.25, then 80 × 0.25 = 20. You multiply by the decimal.
Wrong
€100 + 20% and then −20% should return €100.
Right
€100 × 1.20 = €120. Then €120 × 0.80 = €96. After the rise the base is larger, so 20% of it is more.
Wrong
Computing a discount from the sale price.
Right
discount% = reduction ÷ original price × 100. The original price is 100%.
Wrong
Adding 21% BTW as ÷ 0.21, or as × 0.21 without adding the tax to the net amount.
Right
Incl. BTW = net × 1.21. The tax alone is net × 0.21. Strip tax: gross ÷ 1.21.
Practice
vmbo A bus has 48 passengers. 12 are standing. What percent are standing?
25%
12 ÷ 48 = 0.25 → × 100 = 25%.
vmbo What is 15% of €240?
€36
240 × 0.15 = 36.
havo Followers rise from 3,500 to 4,130. What is the percent increase?
18%
((4,130 − 3,500) ÷ 3,500) × 100 = 18%.
havo A product costs €85 including 21% BTW. What is the price excluding BTW?
€70.25 (rounded to 2 decimal places)
85 ÷ 1.21 ≈ 70.2479 → €70.25. Check: 70.25 × 1.21 ≈ 85.00.
vwo €5,000 grows by 3.5% per year. After how many whole years is the amount larger than €7,500?
12 years
5,000 × 1.035n > 7,500 → 1.035n > 1.5 → n > log(1.5) / log(1.035) ≈ 11.79. After 11 years it is about €7,300; after 12 years it is above €7,500.
Percentages in the Netherlands
BTW is Dutch value-added tax (VAT). The Netherlands uses a standard rate of 21% and a reduced rate of 9% (among other things food and books). Net × 1.21 or × 1.09 gives the price including tax. Those percentages come from the Belastingdienst; check them when you need a current amount.
A percentage point is not the same as a percent. If interest moves from 2% to 5%, that is 3 percentage points, and a relative rise of 150%.
Next step
- How does this work? The explanation and examples are further up this page.
- Test yourself Percentage practice, with an explanation after every answer.
- Video explanations On the Percentage practice page. YouTube only loads when you press play.
Learning path
- Learn first: Fraction calculator Add, subtract, multiply, divide, and simplify fractions.
- Next: Exponential growth calculator Growth factor, N = B · gᵗ, doubling time and half-life.
- Related: Scale calculator
Frequently asked questions
How do you calculate a percentage?
percentage = (part ÷ whole) × 100. 12 out of 80: 12 ÷ 80 × 100 = 15%.
What is X% of Y?
Y × (X ÷ 100). 15% of 80 = 80 × 0.15 = 12.
How do you calculate percent increase or decrease?
((new − old) ÷ old) × 100. From 50 to 65 is +30%. From 80 to 60 is −25%.
How do you calculate 21% BTW (Dutch VAT)?
Incl. = net × 1.21. Excl. = gross ÷ 1.21. Reduced rate: factor 1.09. Check the rate with the Belastingdienst (Dutch tax authority).
How do you find the whole when you know the part and the percentage?
whole = part ÷ percent × 100. Example: 36 is 15% of what? 36 ÷ 15 × 100 = 240.