Overdraft Effective APR Calculator
An overdraft fee is quoted as a flat dollar amount, which makes it look almost harmless, but that framing hides just how expensive overdrafts really are. The honest way to judge any short-term borrowing is to convert its cost into an annual percentage rate, the same yardstick used for loans and credit cards. When you do that with a typical overdraft, the numbers are startling, because the fee stays the same whether you were overdrawn by a few dollars for two days or a few hundred for a month. This calculator performs that conversion. Enter the overdraft fee your bank charged, the amount you were actually overdrawn and how many days the overdraft lasted before you brought the balance back up. The tool divides the fee by the amount to get the cost per dollar, annualizes it over a 365-day year, and reports the effective APR. Seeing a small fee translate into a triple-digit or quadruple-digit annual rate is the clearest possible argument for setting up low-balance alerts or linking a savings buffer. It also lets you compare an overdraft against a credit card, where the cost is already an annual rate. Every figure is computed deterministically, with a worked example below that reconciles exactly to the calculator.
An overdraft APR annualizes a flat fee over the days it covers: APR = (fee / amount) x (365 / days) x 100. A 35 fee on a 100 overdraft repaid in 14 days is an effective APR of 912.50%, far above any credit card.
Overdraft APR formula
APR = (fee / amount) x (365 / days) x 100
fee = flat overdraft fee charged
amount = dollars overdrawn
days = days the overdraft was outstanding
The fee divided by the amount is the cost per dollar borrowed. Multiplying by 365 over the number of days scales that single-period cost into an annual rate.
Worked example
A 35 overdraft fee on a 100 overdraft that you clear after 14 days.
- Cost per dollar = 35 / 100 = 0.35.
- Annualization factor = 365 / 14 = 26.0714.
- APR = 0.35 x 26.0714 = 9.125 (as a rate), times 100.
- Effective APR = 912.50%.
These are the calculator's default inputs, so the result above matches the widget exactly.
Overdraft effective APR calculator: frequently asked questions
Why express an overdraft fee as an APR?
A flat fee looks small, but if it covers only a few dollars for a few days the implied annual rate can be astonishing. Converting the fee to an annual percentage rate puts it on the same scale as loans and credit cards, revealing that overdrafts are among the most expensive ways to borrow.
How is the overdraft APR calculated?
Divide the fee by the amount overdrawn to get the cost per dollar, then scale that up to a year by multiplying by 365 divided by the number of days you were overdrawn. Multiplying by 100 expresses it as a percentage. Short periods and small overdrafts produce the highest APRs.
Are overdraft APRs really that high?
Yes. A 35 fee on a 100 overdraft repaid in two weeks works out to over 900% APR. Because the fee is fixed regardless of the amount or duration, the shorter and smaller the overdraft, the higher the effective rate climbs. This is why regulators scrutinize overdraft pricing closely.
How can I avoid overdraft fees?
Options include opting out of overdraft coverage on debit transactions, linking a savings account for automatic transfers, setting low-balance alerts, and choosing accounts that do not charge overdraft fees. The Consumer Financial Protection Bureau provides guidance on overdraft rights and how coverage works.
What is the overdraft APR formula?
APR equals (fee divided by amount overdrawn) times (365 divided by days overdrawn) times 100. It treats the single fee as the cost of borrowing the overdrawn amount for the days it was outstanding, then annualizes that cost.
Official sources
- Overdraft fees, the cost of short-term borrowing and APR: US Securities and Exchange Commission, Investor.gov. As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.