Investing & Finance

Overdraft interest calculator

Even a few weeks in the red can cost you noticeable money. The calculator shows you the interest charge immediately.

Updated on Apr 21, 2026 Calculator, calculation path and examples on one page

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Calculator

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Calculation path

Step by step

  1. Apply annual interest rate

    Result: 11.90%

    The bank interest rate is calculated down to the actual duration of the loan.

  2. Calculate interest costs

    Formula: Amount × interest rate × days / 365

    Values inserted: €1,800.00 × 11.90% × 30 / 365

    Result: €17.61

  3. Total load

    Formula: Overdrawn amount + interest

    Values inserted: €1,800.00 + €17.61

    Result: €1,817.61

Instructions

How to use this calculator correctly

Input

  • Enter the average overdrawn amount.
  • Take the interest rate from your bank's price list.

Read the result

  • The interest costs only show the financing costs, not possible account management fees.
  • The comparison number for 30 days helps with quick classification.

Practical tip

  • The longer you stay in the red, the more likely it is to get a cheaper loan with fixed installments.

Related guide: ETF, savings plan and compound interest simply explained

Examples

Typical calculations

1,800 euros for 30 days.

Short bottleneck

Interest costs: €17.61

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3,500 euros for 90 days.

Longer overdraft

Interest costs: €107.88

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FAQ

Frequently asked questions

How are overdraft interest calculated?

Banks charge interest on the amount used on a daily basis.

Why is the overdraft facility so expensive?

Because it is very flexible and can be used without a separate credit agreement.

When is an installment loan more worthwhile?

If you use the overdraft facility over several months or with larger amounts.

Are overdraft interest and overdraft interest the same thing?

Not quite. Overdraft interest often applies to amounts above the actual overdraft limit and is usually even higher.

Why does the calculator use 365 days?

This is a common basis for day-to-day interest calculations and is sufficiently precise for an approximate calculation.

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Sources and notes

Rule status and context

Formula
Interest = amount × annual interest × days / 365
Note
Banks sometimes calculate 360 ​​or 365 days. Small deviations are therefore possible.