Back rent calculator: how much rent does my tenant owe?
Add up unpaid rent over several months, with each payment applied to the oldest unpaid month first.
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YYYY-MM, for example 2026-01
YYYY-MM, for example 2026-06
This is an estimate, not legal or tax advice. Check your lease and local rules.
Rules on collecting back rent vary by location. Check your local law and your lease.
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How it works
Enter the monthly rent, the first and last month owed, and each payment with its date and amount. A blank payment row is skipped.
Every month from the first month through the last month owes the full monthly rent. Partial months are not prorated here, so for a move-in or move-out month, use the prorated rent calculator on this site and adjust.
Payments are taken in date order. Each payment goes to the oldest month that still has a balance, and any amount left over moves on to the next month. Money beyond everything owed shows as a credit.
The table shows each month's rent due, the amount applied and the balance left. Back rent owed is the total of the balances left. All math is done in whole cents, so the totals add up exactly.
Oldest-first can surprise: a payment meant for a recent month still clears the oldest balance first, so the recent month can show as unpaid. Your lease or local law may require a different order.
FAQ
How much rent does my tenant owe? Enter the monthly rent, the first and last month owed, and each payment with its date and amount. Every month from the first month through the last month owes the full monthly rent. Back rent owed is the total of the balances left.
Which month does a payment go to? Payments are taken in date order. Each payment goes to the oldest month that still has a balance, and any amount left over moves on to the next month. Money beyond everything owed shows as a credit. Your lease or local law may require a different order.
Does it prorate a move-in or move-out month? No. Partial months are not prorated here, so for a move-in or move-out month, use the prorated rent calculator on this site and adjust.
Does it add late fees? No. The total is unpaid rent only. For a fee on a late payment, use the late rent fee calculator.