Practical money math

Make the numbers make sense.

Fast, transparent financial calculators for everyday planning. Your inputs stay in your browser; every result explains the assumptions behind it.

Six focused calculatorsNo sign-up. No account connection. Educational estimates with visible formulas.

Choose a tool

Plan one decision at a time

Start with the question you need answered.

Investing

Compound Interest

Project a starting balance and monthly contributions over time.

Calculate growth →Investing

Rule of 72

Estimate how long an investment takes to double and compare the exact result.

Estimate doubling →Retirement

FIRE Number

Estimate the portfolio needed to cover an annual spending gap.

Plan independence →Savings

Emergency Fund

Build a cash target around expenses, income stability and dependents.

Set a target →Debt

Snowball vs Avalanche

Compare payoff time and interest under two popular strategies.

Compare methods →Cash

HYSA Growth

Compare high-yield savings with a traditional account using APY.

Compare savings →

Built for clear, cautious estimates.

Local calculation

Calculator inputs are processed on your device.

Visible assumptions

Rates, timing and formulas are explained on each page.

Educational use

Results are planning scenarios, not financial advice.