Interest Calculator

Compare simple and compound interest using your own principal, rate, term, compounding frequency, and optional recurring contributions.

Interest type

Starting principal

Annual rate (%)

Years

Compounding

Monthly contribution

—Final balance

—Interest earned

—Total contributed

—Effective annual yield

—Last month interest

Core borrowing, saving & investing workflows

Start with the broad calculator that matches the decision, then move to a specialist only when the loan structure, cash flow, tax treatment, debt strategy or savings goal genuinely changes.

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Compound-growth scenario ledger

Model a compound-growth scenario with explicit compounding frequency and recurring monthly contribution. Separate principal, deposited contributions and earned interest so the result is useful for scenario comparison rather than being confused with simple interest.

Starting principalAnnual rate (%)YearsCompounds per yearMonthly contribution

—Ending balance

—Total deposits

—Interest earned

—Compound periods

Ready.

Checkpoint	Balance	Deposited principal	Interest component

Recurring contributions are applied monthly in this scenario ledger; the selected compounding frequency applies to the interest rate. This is a mathematical projection, not a quoted account return.

Compare debt and rate scenarios

connects debt payoff, credit-card cost, loan comparison, APR/APY, effective-rate, weighted-rate, and hypothetical consolidation calculations.

Compare assumptions, not offers

Results are deterministic browser-local math from the values you enter. They are useful for scenario comparison, but they are not a lender quote, approval decision, investment forecast, credit recommendation, or substitute for an account agreement.