Effective Interest Rate Calculator
Calculate the effective (real) interest rate on a loan — nominal rate plus origination and periodic fees, converted into one comparable annual cost.
How to use the effective interest rate calculator
- Enter the loan amount and the nominal (stated) interest rate.
- Enter the loan term in years.
- Enter the origination fee (one-time) and any monthly fee.
- Effective interest rate and payment details update automatically.
What is effective interest rate?
The effective interest rate shows the real annual cost of a loan, including all fees — not just the nominal rate that's often advertised. Because you pay an origination fee upfront (which reduces what you actually receive), and possibly a fixed fee each period, the real cost is always higher than the nominal rate alone. Effective interest rate is therefore the number you should use when comparing different loan offers — many countries legally require lenders to disclose it alongside the nominal rate for exactly this reason.
Worked example: $10,000 at a 10 % nominal rate over one year, with a $190 origination fee and $5 per payment, gives an effective rate of 15.76 %. You receive 10,000 − 190 = $9,810 but repay about $10,610 across twelve payments. The fees lift the rate by almost six percentage points precisely because the term is short — the same fees spread over five years would barely move it. It is the effective rate, not the nominal one, that should be compared between offers.
Frequently asked questions
Why is effective rate higher than nominal rate even with no fees?
Because effective rate accounts for the fact that interest is usually paid monthly (a compounding effect over the year), while nominal rate is a simple annual figure. Even a loan with zero fees will therefore have an effective rate marginally higher than the nominal one.
Why is effective rate so much higher on short loans?
Fixed fees (like an origination fee) are spread over fewer years on a short loan, making up a larger share of the annual cost. On a 25-year mortgage the same fee becomes almost negligible in the effective rate, while it can have a large impact on a one-year loan.
Should I always choose the loan with the lowest effective rate?
Effective rate is the best single number for comparing the pure cost of different loans with the same amount and term — but also check other terms, such as flexibility for extra repayments, lock-in periods, and any other conditions.