Mortgages, salaries, health, math and unit conversions, with live charts, local tax rules and links you can share. Everything runs in your browser.
Start with the tools people use most, from mortgages and salaries to BMI, fractions and unit conversions.
Estimate monthly PITI commitments, compare 15 vs 30-year terms, inspect cantonal/state taxes, and download full amortization schedules.
Project asset accumulation with monthly contributions (DCA), inflation adjustment, Rule of 72 doubling timelines, and 5 market presets.
Side-by-side financial comparison of auto loans vs closed-end leasing. Computes true net cost after vehicle depreciation and equity retention.
Calculate percentages of numbers, percentage change/growth, ratios, and reverse pre-discount/pre-tax values with step-by-step arithmetic.
Track 7-day work hours, deduct unpaid lunch breaks, model weekly or daily overtime thresholds, and compute estimated gross payroll.
Instant Imperial & Metric BMI calculation with visual WHO category gauge, age-stratified context, and target healthy weight ranges.
Clinical Mifflin-St Jeor BMR, daily energy expenditure, customizable deficit milestones, and macronutrient distributions.
Calculate calendar days, business working days excluding weekends, exact age milestones, and add/subtract days.
Add, subtract, multiply, and divide mixed numbers and improper fractions with step-by-step common denominators and GCD reduction.
Solve proportions (A:B = C:D), simplify multi-part ratios, scale display aspect ratios (16:9, 4:3), and divide amounts proportionally.
Calculate arithmetic mean, median, mode, range, IQR, variance, and standard deviation with weighted inputs and interactive box plots.
Bidirectional conversion across Celsius (°C), Fahrenheit (°F), Kelvin (K), and Rankine (°R) with visual thermal gauges and physics formulas.
Convert between metric and imperial units (meters, feet, inches, miles, km) with compound feet-inches parsing and architectural fractions.
Calculate cubic yards and 80 lb / 60 lb bags for slabs, footings, post holes, and steps with +10% spillage margin.
Design code-compliant stairs with exact fractional cuts (1/16"), real-time vector CAD blueprint, and IRC R311.7 validation.
Practical guides, calculation formulas, and algorithmic deep-dives from our team.
A comprehensive guide to understanding your paycheck: progressive tax brackets, social contributions, employer labor costs, the tax wedge, and a 20-country global tax comparison.
Why we built Open Calculators — client-side calculation engines, zero data harvesting, and mathematical rigor for finance, health, and everyday life.
Every calculator is free, private and made to answer real questions quickly.
Results update as you type or drag a slider, with charts and schedules that redraw on the spot. No submit buttons, no waiting.
Your inputs are saved in the page link. Bookmark a scenario or send the exact numbers to a partner, client or advisor.
Everything is calculated on your device. No account, no email wall, and nothing you enter is sent to or stored on a server.
Local taxes, currencies and rules: mortgages for 19 countries, plus tools like German Minijobs, Brazilian MEI and Korean severance pay.