About us
A calculator should show its working.
DailyCalc began with a small frustration: almost every calculator on the web returns a number and nothing else. No formula, no assumptions, no indication of when the answer stops being useful. That is fine for idle curiosity and genuinely risky when the number decides a loan, a notice period or a health conversation.
So we built the opposite. Fifteen tools across finance, mathematics, health and time — each one pairing a fast, validated calculator with the formula it evaluates, a fully worked example at realistic magnitudes, the situations where it helps, and the mistakes that make it lie. The result is something you can check, teach from, and argue with.
Everything is free, nothing requires an account, and the maths runs on your own device. We would rather earn trust through method than through marketing.
Our principles
Six rules every page obeys
Show the formula
Every tool publishes the exact expression it evaluates, defines each variable, and states the assumptions baked into it. If you disagree with a result, you can find the disagreement.
Test the maths
Calculation logic is pure TypeScript, isolated from the interface, and covered by an automated unit-test suite that runs on every build. Known-good results are asserted, not assumed.
State the limits
Limitations and common mistakes are mandatory sections. BMI cannot see muscle; loan maths ignores fees unless you add them. We print the gap instead of hiding it.
Collect nothing
Calculators run entirely in your browser. Your salary, weight and date of birth are never transmitted, logged or stored — we could not retrieve them if asked.
Stay independent
No advertising, no sponsored tools, no affiliate lending links. Nobody pays to change a default value or to rank higher in our directory.
Build to scale
Adding a calculator means adding logic, content and a form — never restructuring the site. That discipline keeps quality constant as the library grows.
How a DailyCalc tool gets built
We start from the standard published formula for the domain — the annuity payment formula for amortising loans and EMI, the compound interest formula with a contribution annuity for savings, WHO adult categories for BMI, proleptic Gregorian arithmetic for every date calculation. The maths is written first, as a pure function with no interface attached, so it can be reviewed and tested on its own terms.
Next comes validation. Each function rejects the inputs that quietly produce nonsense elsewhere: zero denominators, percentage change from a zero base, birth dates in the future, minutes above 59, rates outside 0–100%. Instead of returning a misleading figure, it throws a message written for a human being.
Then the guide. A worked example is computed at realistic magnitudes and checked in reverse where a reverse check exists. Use cases are drawn from the situations people actually face — a rent review, a night shift timesheet, a stacked discount code, a school cut-off date. The mistakes section documents the errors we see most: adding stacked percentages, treating 8h 25m as 8.25 hours, extracting GST by multiplication.
Finally the page ships with unique metadata, breadcrumbs, structured data and internal links to related tools — and its calculation logic joins the test suite, where a future change that breaks a known-good result fails the build before anyone sees it. The full process is documented in our editorial policy.
By the numbers
- 15
- calculators live today
- 4
- categories: math, financial, health, time & date
- 24
- automated tests guarding the maths
- 0
- trackers, ads or sponsored placements
What we cover
15 tools organised into four shelves. Each shelf grows independently, so new calculators slot in without disturbing what already works.
Start with these
All 15 calculators
BMI Calculator
Know your Body Mass Index in seconds — with healthy-range context.
Open calculator
Percentage Calculator
What is X% of Y? What % is X of Y? Answered with steps.
Open calculator
Percentage Increase / Decrease Calculator
Old → new percent change, with increase vs decrease explained.
Open calculatorFound a number you disagree with?
Tell us the calculator, your inputs and the result you expected. We re-derive it from the published formula and correct the page if we got it wrong — corrections are the fastest way this library improves.