Annualized Interest Rate Calculator

Use our Annualized Interest Rate Calculator to turn a return earned over days, weeks, months or years into a yearly rate — both simple and effective, side by side — or to find the interest an annualized rate gives over any length of time.

The simple method scales the return in proportion to time; the effective method assumes it keeps compounding at the same pace. For example, $250 on $10,000 in 90 days is a 2.5% return: 10.14% a year simple, or 10.53% a year effective. The shorter the period, the more compounding adds: 2% in 30 days is 24.33% simple but 27.24% effective. Over more than a year it’s the other way round — 50% over 3.5 years is 14.29% simple but only 12.28% effective.

Choose Interest to go the other way: $20,000 at 6% for six months earns $591.26 at an effective rate, or $600.00 as simple interest. Losses work too — a $500 loss on $10,000 in three months is −20% a year simple, or −18.55% effective. A year is 365 days, 52 weeks or 12 months.

Annualizing puts returns on the same yearly scale; it doesn’t forecast them, and a short-period return may not repeat, so treat the results as an estimate. For simple interest on a loan or savings with exact dates, use our Simple Interest Calculator; for the yearly growth between two values over years and months, our Equity Growth Calculator.