How late fees work
A late fee is what a tenant owes when rent arrives after the due date. Leases usually set it as either a flat dollar amount (say $50) or a percent of monthly rent (say 5%). Many leases also give a grace period — a few days after the due date before any fee applies.
This calculator applies the fee only once the days late exceed the grace period. Example: $1,500 rent, a 5% fee, 5 days late with a 3-day grace period → the fee applies and comes to $75.
Watch the state caps
Late fees are one of the most regulated parts of a lease. Many states cap them — often around 5% of rent, sometimes a flat dollar limit, and several require a mandatory grace period. A fee that's legal in one state can be unenforceable next door, so check your state's rules before charging it.
For the state-by-state picture, see our rent laws by state hub. And to make sure the underlying rent is set right in the first place, pull a free rent estimate for the address.