Prorated Rent Calculator (30-Day Banker's Rule vs. Actual Calendar Month)
Calculate your exact partial-month rent when moving in or moving out mid-month—comparing the statutory 30-day uniform method against actual calendar days.
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2. Your result Live Output
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3. How the rule works
Who this is for
Tenants and landlords working out rent for a partial month when a tenancy starts or ends mid-month, and anyone comparing the three common ways of doing the math.
The difference between methods is usually small, but it is a frequent source of disputes in the final month and on deposit statements.
What to have ready
- Your monthly rent.
- The move-in or move-out date, and whether that day counts as occupied.
- The number of days in that calendar month.
- Any pro-rating clause in your lease.
The rule
No statute in most states sets a single method for pro-rating rent. The lease usually controls, and if it is silent the parties use a reasonable method. Three are common: monthly rent divided by 30, monthly rent divided by the actual number of days in that month, and annual rent divided by 365.
Pro-rating often comes up when a month-to-month tenancy ends mid-month. In California, Civil Code § 1946 allows either side to give notice on any day, so the tenancy ends at the end of the notice period, which may fall in the middle of a month. Rent is then owed only through that date. Whatever method is used, it should be applied the same way at move-in and move-out.
Read the official text:
Worked example: 12 days in a 31-day month
Monthly rent is $2,700 and the tenant occupies the unit for 12 days in a 31-day month.
Divide by 30 : $2,700 / 30 = $90.00/day x 12 = $1,080.00 Divide by 31 : $2,700 / 31 = $87.10/day x 12 = $1,045.16 Annual / 365 : $32,400 / 365 = $88.77/day x 12 = $1,065.21 Spread between methods = $34.84
Common mistakes
- Using different methods at move-in and move-out to the landlord's or tenant's advantage.
- Forgetting to include or exclude the move-out day consistently.
- Assuming notice must be given on the first of the month. In many states, including California for month-to-month tenancies, it can be given on any day.
- Leaving a pre-paid partial month off the deposit statement.
Limits of this tool
- The lease, local rules or a written agreement can require a particular method.
- Some subsidised housing programs use their own pro-rating rules.
- The tool does the arithmetic; it does not decide which method your lease requires.
Sources were last checked in October 2026. Statutes are amended often; if the official text differs from this page, the official text controls.
4. Clear Next Steps & Statutory Action Plan
- Look for a pro-rating clause in your lease.
- Count the occupied days, deciding whether the move-out day is included.
- Apply one method and show the calculation in writing to the other side.
5. Frequently Asked Statutory Questions (Cal. Civ. Code § 1947; Standard Residential Lease Accounting Rules)
Which method is cheapest for the tenant?
In a 31-day month, dividing by 31 gives the lowest daily rate; in February, dividing by 30 is lower. The annual method is in between.
Do I owe the whole next month if I give notice on the 10th?
For a California month-to-month tenancy, no. The tenancy ends at the end of the notice period, and rent is owed only to that date. Check the lease and your state's rules elsewhere.
What if I prepaid a full month?
The unused days should be refunded or credited. They often appear on the final deposit statement.
Is the day I move in counted?
Usually yes, because you have possession that day. For move-out, many leases count the last day of possession. Whatever rule you use, apply it the same way at both ends.
Does pro-rating apply to a fixed-term lease?
It applies at the start and end if the term begins or ends mid-month. Leaving a fixed-term lease early is a separate issue governed by the lease and the duty to mitigate.