Money Calculators
Use this monthly interest calculator to translate APR into estimated monthly, daily, and billing-cycle interest.
Live calculator
Balance multiplied by APR divided by 12.
30 days using a daily periodic rate estimate.
Daily periodic rate is 0.0630%.
The monthly shortcut divides APR by 12. Many credit cards and some accounts calculate interest daily, so the billing-cycle estimate uses APR divided by 365 and multiplies by the number of days entered.
Shows the monthly and daily rate used in the estimate.
| Measure | Estimate |
|---|---|
| APR | 22.99% |
| Monthly periodic rate | 1.9158% |
| Daily periodic rate | 0.0630% |
| Billing-cycle interest | $94.48 |
Use this as a planning estimate. Taxes, fees, rates, account terms, provider policies, local rules, and timing can change real-world results.
Quick answer
Monthly Interest Calculator calculates monthly interest from balance, APR, and billing days. The visible formula is Monthly interest = balance x APR / 12; daily interest = balance x APR / 365.
Formula
Monthly interest = balance x APR / 12; daily interest = balance x APR / 365The billing-cycle estimate uses a daily periodic rate, which is common for credit card interest estimates.
How to use
Example
Calculator use
Before relying on it
Details
These notes make the assumptions explicit, especially where the same search query can mean slightly different things.
This is a simple estimate for turning an annual rate into a monthly interest amount.
Many card issuers use a daily periodic rate, so billing-cycle interest can depend on days and daily balances.
Actual credit card interest can use average daily balance, daily compounding, grace periods, and different APRs for different balances.
Source notes
Benchmarks
The calculator is a decision aid, not a fixed rule. Use the output to compare scenarios and document your assumptions. Benchmark ranges are broad planning heuristics unless this page names a specific source for the range.
Good for a quick monthly interest estimate.
Useful for billing-cycle interest when interest accrues daily.
When interest accrues daily, reducing the balance earlier can reduce interest.
Calculator accuracy
The formula, inputs, example, and limitations are shown so the result is checkable, not just a number in a box.
Monthly interest = balance x APR / 12; daily interest = balance x APR / 365
Balance, APR, Billing days
Money results are planning estimates. Actual taxes, account terms, rates, fees, timing, local rules, and provider policies can change the real-world result.
June 6, 2026
Toolkit Shelf. Monthly Interest Calculator. Last reviewed June 6, 2026. https://toolkitshelf.com/tools/monthly-interest-calculator
FAQ
Divide APR by 12, then multiply the monthly rate by the balance.
Divide APR by 365 to estimate a daily periodic rate, then multiply by the balance.
No. Many credit cards calculate interest daily, often based on average daily balance.
No. Use it for planning and comparison. Real decisions can change after exact rates, balances, fees, taxes, account terms, timing, and personal details are verified.
Small changes in rates, payment timing, taxes, fees, balances, or income can materially change the result, so the assumptions need to stay visible.
Different tools may use different rounding, assumptions, default rates, methods, formulas, or input timing. Compare the visible method and inputs before relying on the output.