How we make and check our tools
Last updated: 13 November 2026
SumKitTool publishes free calculators, converters and generators. Every tool is built to answer one question clearly — and to show its working, so you can trust the answer. This page explains how we choose tools, check the numbers and fix mistakes.
How we choose what to build
We build tools people actually search for. Money questions come first — mortgages, tax, salary, debt and savings — for the United States and the United Kingdom, alongside everyday, text and generator tools. We only publish a tool when we can check its maths against a reliable source.
How we check the numbers
- Official sources first. Figures come from official sources named on each page — for example, the IRS and the Social Security Administration for US tax and salary tools, GOV.UK and HMRC for UK tools, and the Freddie Mac Primary Mortgage Market Survey for mortgage rates.
- Worked examples. Our money pages show a worked example with the assumptions used, so you can follow the calculation yourself.
- Tested before publishing. Each calculator's maths is tested against worked examples before it goes live, and re-checked when tax bands, rates or rules change. Mortgage rates are refreshed weekly from Freddie Mac.
- Dates on the page. Money pages show their sources and the date the figures were last reviewed, so you can see how fresh a number is.
What our results are — and are not
Results are estimates based on the numbers you enter and the assumptions shown on the page. They are not financial, tax or legal advice. For a decision that involves real money, check with a qualified professional — or with your lender for a mortgage quote.
What we never do
- We never invent ratings or reviews. There are no star ratings or testimonials on this site.
- We never accept payment to change a result. No tool's answer is sponsored.
- We never see what you type. Every calculator runs in your browser; nothing you enter is sent to us. See our Privacy Policy.
Mistakes
When we get something wrong, we fix it and say so. See our Corrections Policy, or report an error through our Contact page.
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