laskeprosentti

Topic

Maths and formulas

Per cent means one hundredth, and a percentage is in practice a multiplier. Once you take that in, every percentage task turns into an ordinary multiplication or division. The pages in this topic are meant for learning and checking, not just a quick answer.

This topic's calculators

percentage formulasPercentage formulasAll the percentage formulas, examples and rules of thumb on one page.percentage calculatorPercentage calculatorFive modes: percentage of a number, share, reverse calculation, increase and change.excel percentagesExcel percentage formulasReady-made formulas for Excel and Sheets, plus pivot-table percentages.dissertation percentagesPercentages in a dissertationShare of a sample, confidence interval, percentage points and areas.percentage changePercentage change calculatorIncrease, decrease, percentage point and a comparison of two numbers.

Background on this topic

Four basic formulas are enough

Percentage of a number, a share as a percentage, the whole in reverse, and percentage change. Every other formula – discount, increase, VAT, margin, growth rate – is a combination of these. Once you spot which number is the 100% in your task, the right formula finds itself.

For the student and the teacher

The calculators always show the formula with the numbers filled in, so they can be used for checking and teaching too. Exercises with solutions are on the formulas page, and there's a dedicated page for the percentage shares and confidence interval in a dissertation.

Other topics

All the site's calculators are grouped into six topics. The same calculator can belong to more than one, because a percentage calculation is rarely tied to just one situation.

Discounts and prices6Tax and VAT5Salary and work4Loans and interest5Everyday and leisure5

Guides

Frequently asked questions about maths and formulas

What's the easiest rule of thumb for percentages?

A percentage is a multiplier. 25% = 0.25, +12% = a factor of 1.12 and −12% = a factor of 0.88.

How do I work out percentages in my head?

Start from 10% by moving the decimal point one step left, then scale up or down. 10% of 240 is 24, so 5% is 12 and 15% is 36.

Is it written 25% or 25 %?

In UK English the percent sign is closed up to the number: 25%. It's read as "twenty-five per cent".

Can a percentage be over a hundred?

Yes. Over 100% means the part is larger than the reference number. If sales double, the growth is 100%.