Start with the question, not the tool
Most people land here with a specific job. Is this loan worth it? How many words is my draft? Why does my title get cut off in Google? Scroll the categories above, pick the one that fits, and you'll find a calculator built for exactly that job.
We've kept the tools small on purpose. One page, one task, one answer. You won't hit a signup wall, and you won't get a newsletter pop-up before you see a number.
What's inside
There are more than a hundred tools, grouped by what you're trying to do. Money tools cover loans, mortgages, savings, retirement and take-home pay. Business tools handle SaaS metrics, e-commerce profit, freelance rates and hiring costs. Health tools estimate calories, macros and pet ages.
For people who build websites, there are SEO checkers, CSS generators, JSON and regex helpers and color tools. And there's a growing set of everyday converters for length, weight, temperature and time.
- Finance and personal finance: loans, interest, retirement, taxes
- SaaS, e-commerce and freelance: margins, rates, churn, payback
- SEO, web dev and dev tools: audits, previews, generators
- Health, pets and hobbies: estimates and quick references
- Math, units and productivity: converters and planners
Your numbers stay with you
Most calculators run in your browser. What you type is processed on your device. That matters when you're entering salary figures, debts or business margins you'd rather not hand to a stranger.
A few tools, like the On-Page SEO Checker, have to fetch a public page from a server, and their pages say so. Check the individual tool page if you're unsure. You can also watch your browser's network tab while you type and confirm nothing is sent.
How we try to keep answers right
Calculators are checked against worked examples, and rates, fees and tax tables live in dated data files, so a figure traces back to a year. When a rule changes, we update the data and the guide behind it.
No AI produces your result. The same inputs give the same answer each time. Still, treat outputs as estimates. Lenders, tax offices and clinics have the final say, and a professional should confirm anything that matters.
Learn how the math works
Next to the tools sit Learn guides. They explain the formulas with worked examples, so you can check the maths by hand if you want. If a result looks odd, the guide usually shows why.
Found a mistake, or missing a tool? Tell us through the contact page. Requests with a clear use case move up the list.