Interest Calculator
Estimate monthly, daily, or total interest charges on any debt.
Who This Is For
If you want to understand exactly how much your debt is costing you in interest each day, month, or year, this calculator makes it clear. It's helpful for anyone who wants to see the real price of carrying a balance.
Example Scenario
A $10,000 balance at 20% APR costs roughly $167/month in interest alone. That's about $5.48 every single day.
Over 12 months with no principal reduction, you'd pay $2,000 in interest. Every dollar you pay above the interest reduces that cost going forward.
How It Works
This calculator helps you understand how much interest you're paying on your debt in different timeframes.
- Monthly Interest: How much interest accrues each month
- Daily Interest: Daily interest charge (useful for credit cards)
- Total Over Time: Total interest over a specified number of months
Assumptions and Formula
Assumptions used in this model:
- APR is nominal and constant over the selected period.
- No late fees, promo rates, or penalty rates are included.
- Monthly mode uses APR / 12; daily mode uses APR / 365.
Interest formulas: monthly interest = balance × APR / 12, daily interest = balance × APR / 365, and period total = periodic interest × number of periods (if balance is unchanged).
How to Interpret Your Results
| Signal | What It Means | Action |
|---|---|---|
| Daily interest feels high | Debt is expensive even short term | Prioritize principal reduction this month |
| 12-month interest near 20% of balance | Carry cost is materially slowing progress | Evaluate refinance or balance transfer |
| Interest drops sharply with small balance cut | You get immediate payoff from extra payments | Redirect discretionary spend to debt for 90 days |
Frequently Asked Questions
Deep Dive Guide
Read the complete debt interest guide
Understand APR, compounding, and why balances shrink slowly.