One person's calculator collection, built out of [your specific original reason — e.g. "frustration with a mortgage calculator that hid its assumptions"], now free for anyone to use.
I built QuickSum myself to deal with the everyday math problems that kept coming up in my own life — starting with figuring out how currency exchange actually works when the numbers I found online never seemed to agree with each other.
The more I looked at it, the more I noticed how many people are quietly struggling with the same kind of critical finance questions. Inflation keeps climbing. Interest rates keep rising. A lot of us spend a huge share of our working lives just paying down loans, often without a clear picture of what those loans actually cost over time. I wanted a set of tools that made those numbers plain and honest, instead of hidden behind an app trying to sell something.
Each calculator on this site cites its source formula on its own page rather than a black box — for example, the BMI calculator uses the WHO's published thresholds, the calorie calculator uses the Mifflin-St Jeor equation (the version most dietitians actually rely on over the older Harris-Benedict formula), and the currency converter pulls live rates from the European Central Bank rather than a marked-up third-party feed.
[Optional but strong if true: "I periodically check these against a professional tool / spreadsheet I built independently to catch drift." Or mention a specific correction you made after finding an error — a small, honest admission like that does more for credibility than any amount of polished copy.]
Finance, health, and everyday tools — all in one place, all free.
Every calculation runs locally in your browser. We never see the numbers you enter.
Real exchange rates sourced via Frankfurter, which publishes the European Central Bank's official reference rates, updated every 10 minutes.
Works beautifully in any colour scheme, on any screen size.
Health is one of the most important things in life, which is why four of the calculators on this site are built specifically to help you measure and understand basic health numbers — BMI, calories, and body composition among them.
As with everything on QuickSum, these are estimates based on standard published formulas, not medical or financial advice. Use them to understand the numbers, not to replace a conversation with an actual doctor or financial advisor.
QuickSum uses standard, peer-reviewed formulas for every calculation. Our finance calculators use standard amortisation maths and 2024 US tax brackets. Our health calculators use the WHO BMI formula, the Mifflin-St Jeor calorie equation, and the U.S. Navy body fat method.
That said, results are estimates. Real-world outcomes depend on factors our calculators cannot know about — your individual tax situation, lender fees, health conditions, and more. Always verify important decisions with a qualified professional.
Tell me. I check this myself — you're not emailing a support queue.