About us

Why this site exists

Percentage calculations happen every day: in front of a sale sign in a shop, when writing an invoice, in a pay discussion and in the results section of a dissertation. Yet many calculators online give just a number with no reasoning, or have no answer at all to the question "45 is 15% of what?"

We built laskeprosentti.com on three principles:

• Calculator first. The input fields are right at the top of the page. The explanations come after the result, because most people already know what they want to work out.
• Show the formula. Every result shows the calculation with your numbers filled in. That way you can check the sum yourself and don't have to trust a black box blindly.
• Honest limits. The calculator tells you what it works out and what it doesn't. We don't claim to give tax decisions, loan offers, health advice or blood-alcohol estimates.

How the calculators are made

The site is a static HTML site with no user accounts and no back end. All the calculation happens in your own browser. The numbers you enter don't pass through a server, and they aren't stored anywhere except your browser's own memory, if you choose to keep a calculation history.

This is deliberate. It makes the site fast even on a mobile network and removes any need to collect users' pay or tax details. The share links on the salary and tax pages never contain the numbers you entered.

How up to date the information is

The formulas of percentage maths don't change. What does get reconfirmed regularly are the official percentages the calculators use – VAT rates, and National Insurance and pension contributions. We check them at least twice a year and whenever a change in the law is known.

We mark the update date on each page and say what the figure is based on. If you spot outdated or incorrect information, tell us: we'll fix it quickly. For official matters, always use the relevant authority's own service – we are not an official service of HMRC, a bank, a trade union or any other organisation.

Content updated 12 August 2026.

Who is responsible for the content

The content is the responsibility of the laskeprosentti.com editorial team. The calculators' formulas and the UK official percentages (VAT, National Insurance, workplace pension) are checked against sources and tested with unit tests before publication.

The editorial principle is simple: the calculator's logic is written out as a formula, the results are tested with automated unit tests, and the UK official percentages are checked against original sources before a page is published. We don't publish a figure we can't justify ourselves.

The sources we use

The official percentages used in the calculators are based on the following official and expert sources, which are checked as tax periods change:

• HM Revenue & Customs (GOV.UK) – VAT rates (20% / 5% / 0%) and Income Tax rates.
• HMRC / GOV.UK – National Insurance rates (main employee rate 8% in 2025/26).
• The Pensions Regulator – automatic-enrolment workplace pension (minimum 5% employee contribution).
• GOV.UK – Personal Allowance and the Income Tax bands.

Checked 12 August 2026. For official matters, always use the relevant authority's own service; this site is independent and does not represent any of the organisations mentioned.

Citing and linking

May you link to the calculators? Yes, gladly. If you use a calculator in teaching, on a blog or on a forum, you're free to link straight to the right calculator page. A ready-made link:

<a href="https://www.laskeprosentti.com/en/">Percentage calculator (laskeprosentti.com)</a>

If you refer to a calculation result in your text, state the percentage and the date you used, because official rates change. We don't charge for linking and we don't ask for a link back.

Get in touch

Feedback, error reports and requests for new calculators are all welcome: hello@laskeprosentti.com. More details are on the contact page.