Security deposit interest calculator
A dozen-plus states and several big cities require landlords to pay interest on held deposits. Enter the deposit, the rate, and the holding period, and the calculator shows simple and compounded interest side by side.
How this calculator works
Four inputs, two answers:
- Deposit amount: the principal you actually hold, including pet deposits if your jurisdiction treats them as part of the security deposit.
- Annual interest rate: the rate your statute or ordinance publishes. The preset chips cover common jurisdictions, but rates change (some reset every January), so verify the current figure for each year of the tenancy.
- Dates held: from the day you received the deposit to the day you return it (or today, if you're checking accrual mid-tenancy). The calculator counts actual days and converts to years at 365 days per year.
The output shows simple interest (principal × rate × years, what most statutes require) and interest compounded annually (what a few statutes, ordinances, and leases call for) with the gap between them. If you're unsure which applies, the safe play is the higher number: overpaying interest is never a statutory violation, underpaying is.
Who owes deposit interest at all?
Most states don't require it. The obligation typically appears in tenant-protective states (Massachusetts, New Jersey, Connecticut, Minnesota, and others), in specific cities (Chicago is the famous one), or when a lease voluntarily promises it. Some statutes only trigger above a building-size threshold or after the deposit is held for a minimum period: Massachusetts, for instance, owes interest after one year. Where the duty exists, it usually comes with teeth: missing the interest payment can void your right to make deductions or expose you to multiple damages, even when the interest itself is a few dollars.
Caveats
This tool does the arithmetic; it does not know your statute. Published rates change annually in several jurisdictions, some require payment or crediting to rent each year rather than a lump sum at move-out, and some require the deposit to sit in a specific type of account. Check the current rate and payment schedule for your state or city, and when you return the deposit, show your work: principal, rate, holding period, and total, in plain English on the disposition. A tenant who can see the math rarely disputes it.