Calculator Tools
Everyday calculators for VAT, discounts, loans, age, tips, and more — quick and accurate.
About the calculators
This section collects the calculations people actually need to make decisions: what a mortgage, car loan or personal loan will cost each month and in total, how an investment or retirement fund grows under compound interest, what a salary works out to per hour, how much sales tax or VAT sits inside a price, and whether a project's return justifies its cost. The finance set also covers simple interest, payments at any frequency, the rate implied by a payment, break-even, markup versus margin, and payback period. Alongside the money tools are health estimators (BMI, BMR, body fat, ideal weight, daily calorie needs, running pace, sleep cycles, protein intake, net carbs, A1c conversion and a pregnancy due date), maths tools (scientific, fraction, percentage change, standard deviation, confidence interval, triangle, circle, slope, roots, exponents, logarithms, complex numbers, doubling time, a random number generator and a unit converter), everyday helpers for discounts, tips, ages, date intervals and hours worked, grade and GPA calculators for students, technology calculators (subnet, download time, RAID, RAM latency, image file size, PPI), photography calculators (focal length, depth of field, exposure, hyperfocal), and practical planners for concrete, paint, gravel, lumber, pavers, roofing, pipe weight, stairs, air-conditioner sizing, square footage and image aspect ratios.
Each calculator shows the formula it uses, states its assumptions, and where relevant produces a full schedule or breakdown rather than a single number — an amortization table for the mortgage calculator, a year-by-year growth table for compound interest, a per-person split for the tip calculator. Results update instantly as you type, and nothing is sent to a server, so you can experiment freely with real figures.
The tools are grouped by topic below. If you are unsure which to use, the descriptions on each card explain the specific question that tool answers, and the long-form guides cover the concepts behind them: how amortization works, the difference between simple and compound interest, how to read a BMI figure, and how to measure an area correctly before ordering materials.
Guides
Longer articles on the problems these tools solve — what is actually going wrong, what each fix costs you, and which tool to reach for.