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Everyday Money Calculator

Prorated rent, income-based splits, debt payoff timelines, debt-to-income, simple vs compound, and inflation — everyday money math with the rules shown.

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Money questions with exact answers

These six questions have real arithmetic that people guess at: how much rent for 12 days, when this balance actually dies, whether a 28% debt-to-income kills the mortgage. Each member shows its formula and names its convention — because in personal finance the convention is the whole game.

The conventions this page uses

Prorated rent divides by the actual month (leases often use a 30-day year instead). Debt payoff simulates month by month and refuses payments that never touch principal. DTI uses the classic 36% guideline and 43% ceiling. Inflation uses era-average CPI — an estimate, not the BLS index.

Worked example

  1. Debt payoff: $6,000 at 22.9% APR, $250/month.
  2. The simulation runs month by month for about 33 months.
  3. Interest totals roughly $2,100 — over a third of the balance.
  4. At $500/month it clears in about 14 months and saves ~$1,300.

How to use it

  1. Pick the money question from the dropdown.
  2. Enter your numbers — defaults show a typical case.
  3. Read the result and the convention note beneath.
  4. Compare scenarios by editing and watching the live update.

Frequently asked questions

How is prorated rent usually calculated?

Most commonly monthly rent ÷ days in that month × days occupied. Some leases use rent × 12 ÷ 365 × days instead — the difference is small but real; your lease decides.

What DTI do lenders want?

Classic underwriting prefers total debt payments under 36% of gross income; many qualified mortgages allow up to 43%, and some programs stretch to 50% with compensating factors.

Why does my debt payoff say the payment never covers interest?

If the monthly payment is smaller than balance × monthly rate, the balance grows forever — the tool refuses rather than pretend. That situation is worth a credit counselor, not a calculator.

How accurate is the inflation member?

It uses average CPI by era (about 3.3% long-run, 2.5–2.9% recent decades). For exact year-by-year figures use the BLS CPI inflation calculator.

What is the fastest way out of debt?

Mathematically, paying the highest-APR balance first (avalanche) minimizes interest; the snowball (smallest balance first) wins on psychology. Both beat minimums by miles — the payoff member shows the effect of payment size directly.

Does rent split by income make sense?

It is one fairness rule among several. It prevents the lower earner from being priced out of the apartment, which equal splits can do silently.