Quick guide
How to use this calculator
- Enter the balance, rate, timing, fee, or contribution assumptions named by the fields.
- Use one currency and follow the stated nominal, effective, simple-interest, or compounding convention.
- Review the calculator-specific assumptions before comparing accounts or making a savings decision.
Calculation method
Calculation method
Balance compounds monthly at the promotional rate for its entered months, then at the standard rate for the remaining term.
Entered fixed decimals are parsed exactly. Compound projections use stable exponential forms and preserve zero-rate cases exactly; money rounds only for display and a supported nonzero amount is not replaced by a misleading zero.
Worked example
Worked example
A 10,000 balance with 6% promotional interest for 6 months followed by 3% for 6 months produces a blended one-year outcome.
Balance compounds monthly at the promotional rate for its entered months, then at the standard rate for the remaining term.
Supported inputs
Precision and limits
Visible input limits
Amounts accept up to 30 digits and 12 decimal places and are capped at 1e12 per input. Rates are capped at 1000%. Most projections are capped at 1,200 months or 100 years; narrower whole-number limits appear in field labels.
International scope
No currency, institution, current market rate, deposit-insurance rule, tax system, regulatory disclosure, or jurisdiction-specific product term is assumed.
Decision boundary
Results are arithmetic scenarios from visitor-entered assumptions, not account quotations, forecasts, tax advice, legal determinations, deposit guarantees, or recommendations.
Calculator-specific assumptions
Rates, fees, taxes, compounding, crediting, withdrawal, and eligibility terms vary by institution and jurisdiction. This calculator applies only the visitor-entered scenario and does not quote or recommend an account.