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2000+ free calculators, instantly.
Finance, health, math, science, unit conversion, business, food, sports, education, and daily planning. Every calculator includes the tool, formula notes, examples, FAQs, and related guides.
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Five calculator collections
Every calculator is organised into one of five topic areas. Click a collection to browse all the tools, sub-categories, and guides it contains.
Finance
128 calculatorsLoans, mortgages, savings, investments, tax, budgets, retirement planning and more.
Health & Fitness
384 calculatorsBMI, calories, nutrition, body composition, fitness training, sports and wellbeing.
Science & Engineering
752 calculatorsPhysics, chemistry, construction, unit conversion, technology and technical design.
Business & Data
252 calculatorsProfit margins, ROI, pricing, statistics, payroll, revenue and business planning.
Everyday Life
490 calculatorsMath, dates, discounts, tips, education, ecology and everyday household decisions.
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Type any topic — finance, health, math, construction, sports — and results appear instantly below.
Loan Payment Calculator
Free Loan Payment Calculator: calculate loan payment instantly with transparent formula, worked examples and tips. No signup.
Open calculator FinanceEnergy Savings Calculator
Free Energy Savings Calculator: calculate energy savings instantly with transparent formula, worked examples and tips. No signup.
Open calculator HealthCalorie Deficit Calculator
Calorie Deficit Calculator — evidence-based tool to check your calorie deficit. Includes formula, tips, and interpretation guide.
Open calculator MathMargin of Error Calculator
Margin of Error Calculator: solve margin of error problems step-by-step. Clear formula, worked example, and FAQs included.
Open calculator MathSet Intersection Calculator
Set Intersection Calculator: solve set intersection problems step-by-step. Clear formula, worked example, and FAQs included.
Open calculator ConstructionStorm Drain Calculator
Storm Drain Calculator — estimate storm drain for your project. Fast, accurate, free. No signup required.
Open calculator ConversionInches to Centimetres Calculator
Inches to Centimetres Calculator: convert inches to centimetres instantly. Full formula, unit table, and worked example.
Open calculator ConversionForce Newtons Calculator
Force Newtons Calculator: convert force newtons instantly. Full formula, unit table, and worked example.
Open calculator PhysicsPhotoelectric Effect Calculator
Photoelectric Effect Calculator — calculate photoelectric effect with the correct physics formula. Worked example and unit notes included.
Open calculator ChemistryMolecular Formula Calculator
Molecular Formula Calculator — calculate molecular formula using standard chemistry formulas. Worked example with units.
Open calculator ChemistryReflux Calculator
Reflux Calculator — calculate reflux using standard chemistry formulas. Worked example with units.
Open calculator StatisticsSurvival Analysis Calculator
Survival Analysis Calculator: run survival analysis calculations online. Formula, assumptions, and interpretation guide.
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Calculator categories
Each category page works like a focused mini-library with topic clusters, descriptions, internal links, and calculator pages targeting specific search intent.
Finance
Plan loans, savings, investments, taxes, budgets, interest, and everyday money decisions with clear formulas and examples.
128 calculatorsHealth
Estimate health, fitness, nutrition, body measurements, and wellness metrics using practical reference formulas.
134 calculatorsMath
Solve percentages, ratios, fractions, averages, geometry, algebra helpers, and common school or workplace math problems.
130 calculatorsConstruction
Estimate materials, areas, volumes, costs, paint, concrete, flooring, roofing, and renovation quantities.
127 calculatorsConversion
Convert units for length, weight, temperature, speed, volume, area, pressure, energy, and daily measurements.
125 calculatorsPhysics
Work with speed, force, energy, motion, electricity, waves, pressure, and classroom science formulas.
125 calculatorsChemistry
Use chemistry helpers for concentration, molarity, dilution, gas laws, molecular mass, and lab calculations.
125 calculatorsStatistics
Analyze averages, probability, samples, confidence, variation, scores, and data interpretation problems.
125 calculatorsBusiness
Estimate profit, margins, markup, inventory, payroll, pricing, revenue, productivity, and business planning metrics.
127 calculatorsEveryday Life
Quick calculators for dates, time, tips, discounts, travel, fuel, recipes, shopping, and household planning.
110 calculatorsSports
Calculate pace, performance, training zones, scores, ratios, sports statistics, and fitness planning numbers.
125 calculatorsFood
Scale recipes, estimate calories, cooking conversions, ingredient weights, nutrition, and meal planning quantities.
125 calculatorsEcology
Estimate energy use, water use, carbon footprint, recycling, transport impact, and sustainable living metrics.
125 calculatorsEngineering
Work through mechanical, electrical, civil, and systems engineering formulas for practical design checks.
125 calculatorsEducation
Support learning with grade, score, GPA, reading, study time, classroom math, and academic planning calculators.
125 calculatorsTechnology
Estimate bandwidth, storage, download time, screen sizes, data transfer, battery life, and computing metrics.
125 calculatorsAccuracy and transparency
Why United Calculator
Every page follows the same content standard: formula derivation, a worked example with real numbers, applicable laws or professional guidance, 6 plain-language FAQs, and links to 8 related tools.
Verified formulas
Each formula engine is based on published standards — TILA for loan calculations, METS tables for energy expenditure, ASTM standards for materials, and equivalents across 16 subject areas. The formula is shown in a code block on every result card so you can verify the calculation independently.
Professional context, not professional advice
Finance and health calculators cover applicable legislation (CFPB, NHS, OSHA) and reference professional thresholds (e.g. debt-to-income ratios accepted by lenders, WHO BMI categories). Every page includes a disclaimer — these tools are planning aids. Consequential decisions should be reviewed with a qualified professional.
No account, no tracking, no fee
Calculations run entirely in your browser. No data leaves your device. There are no login walls, no usage limits, no subscription tiers, and no premium paywalls. The only data stored is nothing — no cookies are set beyond what your browser requires to render the page.
Transparent methodology
Smart defaults come from published benchmarks — median UK household income from ONS, US average mortgage rate from Freddie Mac weekly surveys, average commute distances from the US Census ACS. Defaults are documented in the article body on each calculator page.
Simple by design
How United Calculator works
Three steps from question to answer — no account, no subscription, no ads cluttering the result.
Search or browse
Type a topic into the search box or click a category. Each category is a mini-library of 125 calculator pages targeting specific questions — loan payments, BMI, tile counts, carbon footprint, and more.
Enter your values
Smart defaults are pre-filled so you get an immediate example result. Replace any field with your own data. Click the ? icon on any field for a plain-language explanation of what that input means.
Read, copy, and share
The result updates in real time. The formula is shown in a code block below the answer. Copy the result to your clipboard, share it to 8 social platforms, or scroll down for the full explanation, FAQs, and 8 related calculators.