Everyday tools that
never leave your device.
Calculators, converters, printables and timers. Each one shows the formula it used, the assumptions behind it, and a dated source.
Check it yourself — open your browser’s network tab. Why this exists
No servers.
There is nothing on the other end to send your work to.
No accounts.
No email, no password, nothing to sign up for.
Works offline.
Once a page has loaded, the tool keeps working with no connection.
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Categories
All tools →Every tool shows its working
How we check →The formula
balance = balance × (1 + r/n)^(n/12) + contributionWritten out, not hidden. If you disagree with the arithmetic you can check it, and if we are wrong you can tell us — corrections are dated in the changelog.
What it assumes
- Contributions arrive at the end of each month
- The return is the same every year
- Tax, platform charges and fund fees are not deducted
They are stated because every one of them makes the real figure different from the one on screen.
Sources
Each source names its publisher, the year it applies to and the date we checked it. A rate that changed last April is a wrong answer, and the date shows when we looked.