CodeASystem calculators

Calculators that show their work.

Free to use173

Practical tools for money, health, math, dates, building, software and everyday decisions. Each one explains the formula, assumptions and limits.

Browse by category

18 collections

Loans, mortgages, savings, investing and debt

Margins, pricing, SaaS metrics and break-even analysis

Pay conversion, overtime, raises and freelance rates

BMI, calories, body composition and pregnancy dates

Pace, lifting maxes, heart rate and calorie burn

Ages, durations, working days and date math

Percentages, fractions, ratios and algebra

Averages, spread, probability and regression

Areas, volumes, angles and distances

Length, weight, temperature, data and speed

Grades, GPA and study estimates

Concrete, paint, tiles, mulch and roof pitch

Recipe scaling, ratios and kitchen math

Fuel, bills, pets and daily-life math

Ads, funnels, conversions and store metrics

Engagement, growth and creator earnings

Footprints, emissions and weather comfort

Encoding, security, networking, cloud and AI cost tools