Calculators

These pages are live, hand-built tools—no app store, no account wall. New calculators land here as they are published.

• Mortgage

  PITI, amortization table, and charts for a home purchase model.

  Open mortgage calculator

• Loan payment (PMT)

  One principal, one rate, one term: monthly payment in seconds.

  Open loan payment calculator

• BMI (adult)

  Metric and imperial, with clear category text.

  Open adult BMI calculator

• Compound interest

  Lump-sum growth with selectable compounding frequency.

  Open compound interest calculator

• Tip

  Gratuity, total with tip, and fair per-person split.

  Open tip calculator

• Calorie (TDEE)

  Mifflin–St Jeor BMR plus activity multiplier.

  Open calorie and TDEE calculator

• Percentage

  Percent of, part vs whole, and percent change.

  Open percentage calculator

• Scientific

  Trig, logs, powers, and constants in the browser.

  Open scientific calculator