Late fee calculator

Choose the method your calculation needs

A flat fee is assessed once when at least one chargeable day remains. Percentage mode also applies once, using the overdue principal as its base. Daily mode multiplies a dollar amount by the number of days after the chosen grace period. An optional cap limits the resulting fee.

These are mathematical options, not recommended lease terms. A calculation does not establish that a fee, grace period or cap is lawful. The guide to “average” rent late fees explains why an unsourced typical amount is not a substitute for checking the applicable rules.

Day-count convention

Days late = max(0, payment date − due date)
Chargeable days = max(0, days late − chosen grace days)

The due date does not count; the payment date does. Weekends, holidays and leap days count as calendar days. This tool does not move a due date or grant an extra grace period because it falls on a weekend.

For a hypothetical April 1 due date and April 10 payment, there are nine days after the due date. If you enter three grace days, six days remain for daily-fee arithmetic. The initial April 2026 dates are an example, not a live payment record.

Worked example with an entered cap

Suppose the chosen terms are $5 per chargeable day, three grace days and a $20 fee cap. With the April dates above, six × $5 gives $30 before the cap; the cap limits the fee to $20. A $1,500 principal would then produce a $1,520 arithmetic total.

Under a separately chosen 2% one-time method, $1,500 × 2% gives $30 once. Under a $25 flat method, the fee is $25 once. These alternative examples do not establish permission to charge any of those amounts.

Money precision and limits

The fee is rounded to the nearest cent, then limited by your entered cap. The form accepts cent-denominated caps; a finer-than-cent cap passed to the calculation is rounded down to keep the fee from exceeding it. A zero cap means zero fee; an empty cap means no cap has been applied by the arithmetic.

The balance stays fixed throughout the date range. Partial payments, changing principal, recurring monthly assessments, interest, compounding and court awards are outside this model. A zero principal gives a zero fee. Use the general prorate calculator for a proportion of a bill, or the net effective rent calculator for lease concessions.

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