InstalmentLoans

Overdraft Cost Calculator

An overdraft cost calculator estimates what an arranged overdraft costs over a set number of days. Enter the amount overdrawn, the yearly interest rate, the number of days and any monthly fee to see the interest, fees and total.

By the InstalmentLoans Editorial Team · Last updated 2 October 2026

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Enter your numbers and press Calculate. Nothing you type leaves your browser.

How this calculator works

Most UK banks charge a simple annual interest rate on an arranged overdraft, rather than the monthly compounding used on loans.

Interest = balance * (annual rate / 100 / 365) * days.

Fees = monthly fee * number of months charged, where a part month counts as a full month.

Total cost = interest + fees.

Overdraft pricing varies widely between banks, so use the rate and fees from your own account.

Frequently asked questions

How do UK banks charge for an arranged overdraft?
Most charge a simple annual interest rate on the amount you are overdrawn, and some add a fixed daily or monthly fee. The exact pricing is set out in your account terms.
Why is the annualised cost different from the headline rate?
The headline rate is the interest rate alone. The annualised figure also includes fixed fees spread across the balance you actually used, so it can be higher.
Is an overdraft cheaper than a loan?
Not necessarily. Overdrafts are designed for short-term gaps, while loans spread a fixed amount over a set term. If you stay overdrawn for months, compare the total cost with a personal loan.
What if I go over my arranged limit?
Unauthorised overdrafts usually cost more and can affect your credit file. This calculator models an arranged overdraft only.

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