Before writing the letter, price the alternative. Take the monthly rent, divide by 30, and multiply by the number of days the unit would sit empty between this tenant and the next one. Add what a turn costs you in paint, cleaning, and locks. That total is what a departure is worth, and it is the ceiling on how aggressive the increase can sensibly be.
Most landlords never run that number. They pick a percentage that sounds normal, send it, and find out in thirty days whether they guessed right.
The turnover math, with real inputs
Use your own figures. Here is the shape of the calculation on a unit renting for $2,000 a month, with a proposed increase of $100.
| Line | Amount |
|---|---|
| Increase, over twelve months | $1,200 |
| Vacancy, 21 days at $66.67 a day | $1,400 |
| Turn costs (paint, clean, locks, minor repairs) | your number |
| Listing, showings, screening, lease prep | your time |
The increase is worth $1,200 a year. Three weeks of vacancy alone gives back more than that, before anyone touches a paint roller. That is why a $100 increase on a tenant who might leave is a worse trade than a $50 increase on a tenant who will stay.
Two inputs decide the whole thing, and both are local to you.
The first is how long the unit really takes to fill. Not how long you hope. Look at your last two turns and count the days between the old lease ending and the new rent starting.
The second is turn cost. Pull the actual invoices from the last turnover instead of estimating from memory. If you track repair spend by unit, that number is already sitting in your records: tracking vendor invoices and repair costs covers how to keep it there.
Where the market number comes from
The math above tells you what you can afford to risk. It does not tell you what the unit is worth. For that, pull three to five current listings within a mile, same bedroom count, same rough condition, and use asking rents from the last thirty days. Older comps and Zestimate-style averages are not evidence of anything a tenant will pay this month.
If the market rent is far above what your tenant pays, you have a choice to make rather than a calculation to run. Closing a large gap in one step is the fastest way to trigger a move. Closing it over two or three annual increases keeps the unit occupied while the rent catches up.
The notice periods are not optional
How much warning a tenant gets is set by statute, and the number changes with the size of the increase and how long they have lived there.
California ties it to the size of the raise. Stay at or under 10 percent and a month-to-month tenant gets 30 days’ written notice before the new rent starts. Go above 10 percent, counting every increase over the prior twelve months, and the notice becomes 90 days (Cal. Civ. Code § 827(b)).
New York ties it to tenure instead. Under Real Property Law § 226-c the notice runs 30 days for a tenant of less than a year, 60 days from one to two years, and 90 days beyond that, triggered by any increase of 5 percent or more.
Those are two of fifty answers. Read your own state’s notice statute before the letter goes out, and California landlords should also check whether the unit falls under the statewide cap: the AB 1482 rent increase limits page carries the formula and the exemptions, and the AB 1482 calculator runs your numbers against it.
Local rules stack on top. Los Angeles, San Francisco, San Jose, and Sacramento all have their own ordinances, and a city cap beats a state cap when the city’s is tighter.
This is general information, not legal advice. Rules change and local ordinances vary. Confirm current requirements with your city, county, or an attorney before you act.
Write it like a landlord, not a form letter
A rent increase notice has to satisfy the statute. The email that goes with it is where the tenancy is kept or lost, and it needs four things.
- The number and the date. New rent, first month it applies, nothing buried.
- A reason that is true. Property taxes, insurance, the new roof. Not “market conditions.”
- What they get. If anything is being fixed, replaced, or added this year, say so here.
- An opening. One line inviting a reply. Most tenants never take it, and the ones who do are telling you something worth hearing.
Keep it under 200 words. A long explanation reads like an apology, and an apology invites a negotiation you did not intend to start.
When to hold the rent flat
Some tenancies are worth more than the increase. A tenant who pays on the first, reports a leak the day it starts, and has been there four years is subsidizing you already in avoided vacancy and avoided repair escalation.
Hold flat, or take a smaller step, when any of these is true:
- The unit has an open habitability issue you have not fixed yet
- You are within 90 days of a planned sale or refinance that a vacancy would complicate
- The tenant is at the top of the local market already
- You would not be able to re-rent quickly at this time of year
That last one is seasonal and specific. A December vacancy in a college town is a different risk than a June vacancy, and the same increase carries different odds in each.
After the tenant says yes
Update the lease record, not just your memory. The new amount has to flow into the rent charge, the autopay enrollment, and any prorated month if the effective date lands mid-cycle. A tenant on autopay who gets charged the old amount for three months after an increase is a collections problem you created.
Handle the paperwork the same way. If the increase comes with a new fixed term rather than a continuing month-to-month arrangement, that is a renewal, and the renewal letter is a different document from a rent increase notice. Ending the tenancy instead is a third path with its own notice periods (Cal. Civ. Code § 1946.1), and it is rarely the cheaper one.