Basic Calculator · Practical guide
How to Calculate Percentage Without a Percent Button
Any percentage becomes a decimal when you divide by 100 — after that it is one multiplication.
At a glance
The Core Trick
A basic calculator has no % key, but you do not need one. Divide the percentage by 100 to convert it to a decimal, then multiply. To find 35% of 240: 35 ÷ 100 = 0.35, then 0.35 × 240 = 84. Two operations, done.
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Enter your own values, then compare the result with the examples below.
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Common Percentage Jobs
- Discount: 25% off a $68 jacket: 68 × 0.25 = 17 off, so you pay 68 − 17 = $51.
- Sales tax: 8% on a $45 purchase: 45 × 0.08 = 3.60, total $48.60.
- Test score: 42 out of 50 correct: 42 ÷ 50 = 0.84, then 0.84 × 100 = 84%.
Shortcut for Discounts
Instead of subtracting, multiply by what remains. A 25% discount means you pay 75%, so 68 × 0.75 = 51 in a single step. Likewise, adding 8% tax means multiplying by 1.08: 45 × 1.08 = 48.6.
Going the Other Direction
To ask "what percent is 18 of 72?", divide the part by the whole and multiply by 100: 18 ÷ 72 = 0.25, then 0.25 × 100 = 25 — so 18 is 25% of 72. Every percentage problem is just a multiply or divide once the numbers are in decimal form.
Frequently Asked Questions
Why does dividing by 100 work?
Percent literally means per hundred. 35% is 35 out of 100, which is the fraction 35/100, or 0.35 as a decimal — ready to multiply.
How do I calculate a percentage increase?
Multiply by 1 plus the decimal rate. A 5% raise on $52,000 is 52000 × 1.05 = $54,600.
What is the fastest way to find 10% of something?
Move the decimal point one place left. 10% of 240 is 24, and you can build 20% or 5% from there.
How do I reverse a percentage?
Divide by the multiplier instead of multiplying. If $48.60 includes 8% tax, the pre-tax price is 48.60 ÷ 1.08 = $45.