Prorated Rent Defined Under California Law
To prorate is to allocate a charge proportionally. In rentals, prorated rent splits the monthly price into a statutory daily amount so tenants pay only for days they occupy the unit. California security-deposit rules use similar logic, but prorating applies to rent, utilities, pet fees, and even late-fee reductions. True prorating uses a consistent daily rate; simply knocking off “a few hundred bucks” is not the same thing.
When Prorating Is Used
You will encounter prorating during mid-month move-ins and move-outs, roommate swaps, lease assumptions, and meter-based utility resets. California landlords typically calculate partial-month rent on the statutory 30-day basis—even for February or 31-day months—because Civil Code §1947 references a “month” as a uniform unit. If you sign on the 28th, paying the full month may violate Civil Code §1671(b) against unreasonable liquidated damages.
How to Calculate Prorated Rent
Step 1: Convert monthly rent to a statutory daily rate by dividing by 30.
Step 2: Count chargeable days—include the move-in day, exclude the move-out
day.
Step 3: Multiply daily rate by the chargeable days.
Example: Monthly rent $2,100. Tenant moves in on August 13. Daily rate = $2,100 ÷ 30 = $70. Days occupied: 18 (Aug 13–30). Prorated rent = 18 × $70 = $1,260.
| Move-In Day | Days Charged | Daily Rate (2400 ÷ 30) | Prorated Rent |
|---|---|---|---|
| 3rd | 28 | $80 | $2,240 |
| 10th | 21 | $80 | $1,680 |
| 18th | 13 | $80 | $1,040 |
| 25th | 6 | $80 | $480 |
Prorated Rent Calculator – California 2025
Legal Considerations
California Civil Code §1947(a) states that rent is payable at the end of the term unless otherwise agreed. A prorate clause must therefore be in writing—usually in Section 4 of the lease or an addendum—and should spell out the exact daily-rate formula. Landlords cannot secretly inflate the divisor (for example, using 28 days to raise the daily rate) nor charge for non-habitual days like picking up keys before the lease begins.
Prorating also touches utility billing. If your lease bundles electricity or water into a flat monthly fee, that charge should be prorated alongside rent when you occupy for only part of a month. Civil Code §1940.9 requires transparency in utility pass-throughs, so ask for the daily rate in writing if utilities are included. Early-termination fees, another partial-month cost, must also follow the statutory 30-day logic. A landlord cannot impose the full month’s rent plus a penalty when you lawfully break a lease with notice; the fee must be “reasonable” and proportionate to actual loss. Courts have repeatedly struck down flat “one-month” early-out charges when vacancy loss was far less. Always compare any early-termination line item against the prorated rent you would otherwise owe and negotiate accordingly.
Common Mistakes
- Forgetting that security-deposit caps factor in prorated rent—see our deposit guide.
- Rounding daily rate to the nearest dollar instead of cents, leading to over-charges.
- Charging February’s 28th or 29th day at a higher daily rate.
- Including move-out day in the count—exclude it by default to stay compliant.
- Mishandling leap-year math: February 29 is still a chargeable day but the divisor remains 30 under state law, not 29.
Tenant Rights & Best Practices
- Before You Sign: Ask the landlord to spell out the formula in the lease. A quick sentence prevents disputes.
- On Move-Out Day: Take meter photos, request move-out prorate in writing, and give a forwarding address as Civil Code §1962 requires.
Example Scenario: Mid-Month Move-Out
Imagine your lease runs month-to-month at $1,800. You give a proper 30-day notice but end up handing back the keys on July 20 instead of July 31 because your new place is ready early. Under California’s uniform 30-day formula, the daily rate is $1,800 ÷ 30 = $60. Because the move-out day is excluded, you pay for July 1–19—exactly 19 days. Multiply 19 × $60 and your final rent obligation is $1,140. Your landlord cannot charge the remaining 11 days unless the lease expressly states a minimum monthly charge regardless of occupancy—a clause courts often deem “liquidated damages” and strike down. Document the key return with a photo and ask for a written confirmation of the prorated amount. This same math applies if you surrender possession due to a negotiated early-termination agreement: rent only accrues through the last full day you hold the unit.