Late Fee & Penalty Interest Calculator
Estimate what an overdue amount costs once a flat late fee and penalty interest are added, period by period.
Quick answer
Late cost is a flat fee charged after the grace period plus penalty interest on the unpaid amount for each day beyond it. Interest is either simple, with a constant daily amount, or compounding monthly on the growing balance.
Late Fee & Penalty Interest Calculator
Total Owed
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Penalty Interest
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Late Fee Charged
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Extra Cost
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Extra as % of Amount
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Breakdown by 30-Day Period
| Period | Days | Interest (₹) | Interest to Date (₹) | Amount + Interest (₹) |
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Assumptions & method
- Penalty days = days late − grace days (never below zero). Nothing is charged if penalty days are zero.
- Simple: interest = amount × annual rate × penalty days ÷ 365.
- Compounded monthly: each 30-day period adds balance × annual rate ÷ 12; a partial last period is prorated by days ÷ 30.
- The flat late fee is charged once when days late exceed the grace period, is not subject to interest and is added to the total.
- Caps, repeating fees, different day counts and local rules are not included. Estimates only, not legal or financial advice.
Results are estimates based on the figures you enter. They are not guarantees and not financial advice.
What lateness costs
When a payment is overdue, two charges commonly apply. A flat late fee is added once the grace period passes, and penalty interest accrues on the unpaid amount for each day beyond it. Interest can be simple, where the same daily amount accrues throughout, or compounding, where unpaid interest joins the balance every month and starts earning interest itself. This calculator counts the days beyond the grace period, applies the method you choose, and splits the result into a period-by-period breakdown so you can see where the cost comes from.