On every single page, not just the popular ones
That is the difference between a calculator and an answer you can act on. Look up a mortgage payment here and you will also learn what PITI leaves out, when PMI actually comes off, and why the APR is not the rate — the things that decide whether the number in front of you is the one you needed.
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41 fields, from mortgage amortisation to duct static pressure to Hardy–Weinberg equilibrium to the cost of a million GPU tokens.
See all A–Z →Tools for consumers, borrowers, loan officers, financial coaches and personal-finance students who need to price debt, compare…
Tools for investors, financial planners, retirees and finance students who need to project portfolio growth, price fixed-income…
Tools for the discounted cash flow, cost of capital, ratio and valuation math that investment bankers, equity analysts, FP&A…
Tools for turning balance sheets, income statements and cash flow statements into the liquidity, activity, solvency…
Calculators for the money math that founders, marketers, sales teams, accountants and online sellers run every day: pricing and…
Tools for anyone who has to turn tax law, wage rules and insurance contracts into an actual dollar figure: taxpayers and…
Tools for the numbers that drive property decisions: cap rates, cash flow, loan sizing, valuation, rehab budgets, lease…
Core numeric and symbolic math tools used every day by middle-school through university students, teachers writing worked…
Tools for computing lengths, angles, areas, volumes and coordinates of plane and solid figures, from classroom Euclidean…
Statistics and probability calculators for students, researchers, data analysts, quality engineers, marketers running…
Tools for the higher-mathematics workflow shared by calculus and differential-equations students, engineering and physics…
Classical and modern physics calculators covering kinematics, forces, energy, rotation, gravitation, oscillations, waves…
Calculators for the quantitative work of chemistry: stoichiometry, solution preparation, gas behavior, acid-base and…
Tools for bench scientists, molecular biologists, microbiologists, clinical laboratory technologists, nurses, pharmacists and…
Tools for licensed electricians, electrical contractors, engineers, apprentices and inspectors who size conductors, motors…
Calculators for HVAC contractors, service technicians, mechanical designers, energy raters and building science students who…
Sizing, flow, pressure and capacity math for plumbers, pipefitters, mechanical and civil engineers, irrigation and pump…
Quantity takeoff, layout geometry, framing math and structural sizing tools used every day by concrete finishers, framers…
Shop-floor and engineering math for machinists, CNC programmers, welders, sheet metal fabricators, tool and die makers…
Engine builders, tuners, racers, performance shops, diesel and fleet technicians, and automotive students use these calculators…
Tools for private, commercial and airline pilots, flight instructors, dispatchers, A&P mechanics, homebuilders, UAV operators…
Calculators for row-crop and forage farmers, ranchers, agronomists, custom applicators, irrigation designers, extension agents…
Tools for personal trainers, dietitians, strength and conditioning coaches, running and triathlon coaches, nurses and midwives…
Working math for bakers, chefs, butchers, charcutiers, caterers, baristas, homebrewers, winemakers and bartenders who turn…
Practical calculators for consumers, renters, homeowners, roommates, parents, travelers and pet owners who need a fast…
Calculators for calendar and clock arithmetic, time systems, solar and lunar geometry, celestial mechanics, telescope optics…
Exact, standards-based converters for the units people actually work in: metric-imperial length and volume, mass and density…
Tools for network engineers, sysadmins, cloud and DevOps/SRE practitioners, storage and backup admins, security analysts…
Calculators for students, teachers, professors, school administrators, tutors, school psychologists and admissions counselors…
Calculators for athletes, coaches, statisticians, fantasy and betting players, tabletop and video gamers, shooters, archers…
Calculators for makers who buy materials by the yard, gram, board foot or spool: knitters, quilters, garment decorators, resin…
Calculators for solar installers, energy auditors, renewable-energy engineers, sustainability analysts, stormwater and…
The sizing, cost and evaluation arithmetic that AI engineers, ML practitioners and technical founders do before renting a GPU…
Technology bought by the hour, the seat and the gigabyte, priced the way finance will eventually read it. A commitment discount…
The money and file-size arithmetic behind making content for a living: what a view, a listener or a subscriber is actually…
The money-and-time arithmetic of a renovation, as opposed to the material takeoffs that sit under Construction & Carpentry…
Calculations for warehousing, freight and trucking, lean production, packaging, mining and aggregates, oil and gas, industrial…
How much cover a person or a business actually needs, what each choice costs, and what a claim really pays. Insurance is priced…
The arithmetic that runs underneath a legal matter, worked explicitly rather than left to a rule of thumb. What a settlement…
The arithmetic musicians and audio engineers actually do: turning tempo into delay and reverb times, note names into…
The specific calculations set by professional licensing and certification exams, and used daily by the practitioners who pass…
Every page states the equation it uses in real mathematical notation, defines each variable with its units, and names the standard or text it came from. All 1,292 of them — a calculator without a stated method does not get published.
Each calculator carries a numeric example with the arithmetic written out step by step, so you can reproduce the result on paper and take away the method rather than just the number.
Imperial and metric side by side with exact conversion factors, defaults chosen for the real job, limits tied to the governing code where one exists, and a print layout that survives being carried to the site.
Every calculator ships with test cases whose expected values come from code tables, standards and textbook problems, and the whole suite is run in a real browser before a build goes out. Read how we calculate for the method.
How this site is made. 4Calculators is built by one person, Michael A. Levy, and the calculators are written with AI (Claude Opus 5) against a specification written for each page, then verified by an automated test suite that runs every calculator's test vectors before publication. Many pages have been personally reviewed; with 1,292 of them, not all have. The about page and the editorial policy say exactly what that means and what it does not.