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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

137 calculators

Loans, mortgages, savings, investments, tax, budgets, retirement planning and more.

Finance
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Health & Fitness

385 calculators

BMI, calories, nutrition, body composition, fitness training, sports and wellbeing.

HealthSportsFood
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Science & Engineering

755 calculators

Physics, chemistry, construction, unit conversion, technology and technical design.

ConstructionConversionPhysicsChemistryEngineeringTechnology
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Business & Data

252 calculators

Profit margins, ROI, pricing, statistics, payroll, revenue and business planning.

StatisticsBusiness
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Everyday Life

491 calculators

Math, dates, discounts, tips, education, ecology and everyday household decisions.

MathEveryday LifeEcologyEducation
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Browse by category

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.

137 calculators

Health

Estimate health, fitness, nutrition, body measurements, and wellness metrics using practical reference formulas.

135 calculators

Math

Solve percentages, ratios, fractions, averages, geometry, algebra helpers, and common school or workplace math problems.

131 calculators

Construction

Estimate materials, areas, volumes, costs, paint, concrete, flooring, roofing, and renovation quantities.

130 calculators

Conversion

Convert units for length, weight, temperature, speed, volume, area, pressure, energy, and daily measurements.

125 calculators

Physics

Work with speed, force, energy, motion, electricity, waves, pressure, and classroom science formulas.

125 calculators

Chemistry

Use chemistry helpers for concentration, molarity, dilution, gas laws, molecular mass, and lab calculations.

125 calculators

Statistics

Analyze averages, probability, samples, confidence, variation, scores, and data interpretation problems.

125 calculators

Business

Estimate profit, margins, markup, inventory, payroll, pricing, revenue, productivity, and business planning metrics.

127 calculators

Everyday Life

Quick calculators for dates, time, tips, discounts, travel, fuel, recipes, shopping, and household planning.

110 calculators

Sports

Calculate pace, performance, training zones, scores, ratios, sports statistics, and fitness planning numbers.

125 calculators

Food

Scale recipes, estimate calories, cooking conversions, ingredient weights, nutrition, and meal planning quantities.

125 calculators

Ecology

Estimate energy use, water use, carbon footprint, recycling, transport impact, and sustainable living metrics.

125 calculators

Engineering

Work through mechanical, electrical, civil, and systems engineering formulas for practical design checks.

125 calculators

Education

Support learning with grade, score, GPA, reading, study time, classroom math, and academic planning calculators.

125 calculators

Technology

Estimate bandwidth, storage, download time, screen sizes, data transfer, battery life, and computing metrics.

125 calculators

Accuracy 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.

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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.

Currency Exchange Calculator

Convert between major world currencies. Includes bank spread cost estimator and round-trip conversion loss.

A currency exchange calculator converts an amount from one currency to another using the current mid-market exchange rate. It is used for travel budgeting, international transfers, import/export pricing, overseas property transactions, and comparing costs across countries. The mid-market rate (also called the interbank rate) is the midpoint between buy and sell rates used by banks — it is the fairest reference rate, but it is not the rate consumers receive from banks, travel money providers, or transfer services, all of whom apply a spread or fee on top. and are useful for related international finance calculations.

Exchange rates fluctuate continuously during market hours, driven by interest rate differentials, inflation, trade balances, political events, and market sentiment. For large transactions, even a 1% movement in exchange rate can represent significant sums — making rate timing and currency risk management important. Specialist currency brokers typically offer significantly better rates than banks for transfers above a few thousand in local currency.

  1. Enter the amount to convert.
  2. Select the source currency and target currency.
  3. The result shows the converted amount at the indicative mid-market rate.
  4. For real transactions, subtract the provider's margin: banks typically 2–4%; specialist transfer apps 0.2–1%; travel money bureaux 2–5%; airport bureaux 4–8%.
  5. For large international transfers, compare rates from specialist providers against your bank — the difference on a large transfer can exceed 1,000 in any currency.
  6. For regular payments (overseas mortgage, international salary), consider a forward contract to lock in today's rate for future delivery.

Currency conversion formula

Converted amount = Source amount × Exchange rate (source → target)

Effective rate after spread = Mid-market rate × (1 − spread%/100)

True cost of conversion = (Mid-market rate − Effective rate) × Amount

Worked example: Converting 10,000 to a foreign currency at mid-market rate of 1.27. Result at mid-market: 12,700. Bank applies 2.5% spread: effective rate = 1.27 × 0.975 = 1.238. You receive 12,380. Hidden cost = 320. Using a specialist app at 0.4% fee: 12,649 received, total fee approximately 40 — a saving of approximately 280 on this transaction.

Understanding your exchange result

Provider spread comparison

Typical total cost (spread + fees) for a 10,000 currency conversion: high-street bank (branch) — 3–5%; bank online transfer — 2–3.5%; PayPal — 3–4%; travel money bureau (airport) — 4–7%; travel money bureau (pre-ordered online) — 1–2.5%; specialist transfer apps (Wise, Revolut) — 0.3–0.6%; specialist currency broker — 0.5–1% with no transfer fee above typical minimums. For transfers above 25,000, specialist brokers often provide dedicated support, forward contracts, and rate alerts that can add further value.

Finance tips and best practices

Common mistakes to avoid

Currency exchange and international money transfer services are regulated in most jurisdictions. Providers must typically be registered with the relevant financial regulator and comply with anti-money laundering (AML) regulations. Large international transfers may require documentation of the source of funds. Always verify that your currency exchange provider is properly authorised before transferring significant sums. Exchange rates and fees shown are indicative only. This calculator is for planning and informational purposes only and does not constitute financial advice.