Pro Rata Calculator
Calculate pro rata (proportional) amounts for any scenario, prorated rent for a partial month, prorated salary for a new hire, refunds for cancelled subscriptions, vacation accrual, dividend distributions, and more.
Reviewed & updated for 2026 by Rakesh Choudhary, PhD · How we calculate
Common pro rata scenarios
Prorated rent (partial month)
Monthly rent ÷ days in month × days lived. For $2,400/month rent, moving in March 20th in a 31-day month: daily rate = $2,400 ÷ 31 = $77.42. Days in unit = 12 (20th-31st). Prorated rent = $929. Some landlords use 30-day standard regardless of month length.
Prorated salary (new hire)
Annual salary ÷ 12 × partial-month proportion. For $75,000 salary starting on the 15th of a 30-day month: $75K ÷ 12 = $6,250 monthly. Days worked = 16 (15th-30th). Pro rata = $6,250 × (16/30) = $3,333 for that month.
Subscription refund
Annual subscription $1,200 paid Jan 1. Cancel Sep 15 (Day 258). Days remaining = 365 - 258 = 107. Refund = ($1,200 × 107) ÷ 365 = $352. Some services charge cancellation fees.
Insurance refund (mid-policy cancellation)
Annual premium $1,800. Cancel after 4 months. Refund = $1,800 × (8/12) = $1,200. Subject to short-rate penalty in some policies (~10% additional fee for early cancellation).
Vacation accrual (mid-year hire)
15-day annual vacation, start July 1 (6 months in). Pro rata allotment = 15 × (6/12) = 7.5 days for the rest of the year. Most employers round to nearest half-day.
Dividend distribution
$10,000 dividend pool distributed pro rata across 1,000 shares. Per-share dividend = $10,000 ÷ 1,000 = $10. If you own 50 shares, your dividend = 50 × $10 = $500.
The 30-day vs actual-days debate
When you prorate something that resets monthly — rent, insurance, subscriptions — you have to choose what counts as a "month." There are two main conventions, and they produce slightly different results.
| Month | 30-day method (per day) | Actual-days method (per day) | Who benefits |
|---|---|---|---|
| February (28 days) | $80.00 | $85.71 | Tenant under 30-day |
| April (30 days) | $80.00 | $80.00 | Neutral |
| July (31 days) | $80.00 | $77.42 | Landlord under 30-day |
All figures based on $2,400/month rent. The 30-day method is simpler and used by most US landlords for residential rentals. Many commercial leases and most insurance contracts use actual-days. Banks and financial institutions typically use a 360-day year (12 × 30) for interest calculations because it simplifies math across products.
If your lease, employment agreement, or contract doesn't specify, ask. The difference can be $20-$50 per partial month for typical residential rent — small numbers but worth getting right.
Pro rata in equity deals: anti-dilution and rights
In startup financing, "pro rata" has a specialized meaning. A pro rata right gives an existing investor the option to participate in future financing rounds at a level that preserves their ownership percentage. Without one, every new investor dilutes earlier shareholders.
Worked example. You hold 5% of a startup. The company raises a Series B and issues new shares equal to 20% of the post-money cap table. Without a pro rata right, your stake drops to 4% (5% × 80%). With a pro rata right, you can invest enough in the new round to keep your 5%.
For early-stage investors, exercising pro rata rights in later rounds is often the highest-return investment they'll ever make — it lets them double down on companies that have already proven traction. For founders, granting unlimited pro rata rights to early investors can crowd out future strategic investors. Most modern term sheets cap pro rata participation at the original ownership percentage or require a minimum check size.
In bankruptcy, "pro rata distribution" means unsecured creditors get paid in proportion to the size of their claims if assets don't cover everyone. Same math, very different stakes.
FAQs
What does pro rata mean?
Pro rata (Latin: 'in proportion') means dividing something proportionally based on time, share, or eligibility. In practice: paying for only the days you actually used a service, owning a share of profit equal to your ownership percentage, or being refunded for the unused portion of a subscription.
How is prorated rent calculated?
Daily rent × days lived = prorated rent. To get daily rent: divide monthly rent by days in the month (some landlords use 30 days as a standard divisor). Example: $2,400/month rent. Move in on the 20th of a 30-day month. Daily rent = $2,400 ÷ 30 = $80. Days in unit = 11 (20th-30th). Prorated rent = $80 × 11 = $880.
What's the difference between 30-day and actual-days proration?
30-day method uses 30 days regardless of actual month length. Actual-days method uses 28/30/31 depending on the calendar month. Actual-days method is more precise but slightly favors the landlord in 31-day months (smaller daily rate) and the tenant in 28-day months (larger daily rate). Most landlords use 30-day for simplicity; check your lease.
How is prorated salary calculated for a new hire?
Annual salary ÷ working days per year × days worked. For a $75,000 salary starting March 14th in a year with 261 working days: daily rate = $75,000 ÷ 261 = $287.36. If 209 working days remain, prorated salary = $287.36 × 209 = $60,058. Most companies use a simpler version: salary ÷ 12 months × proportional days in the partial month.
How does pro rata work for refunds?
(Days remaining in subscription ÷ total days in subscription) × original price. Annual subscription $1,200 paid Jan 1. You cancel Sep 15. Days used: 258 (Jan 1 to Sep 15). Days remaining: 365 - 258 = 107. Refund = (107 / 365) × $1,200 = $352. Some services charge cancellation fees that reduce the refund.
What is pro rata vacation accrual?
If a full year's vacation is 15 days, and you started July 1 (6 months into the year), your prorated allotment is (6 / 12) × 15 = 7.5 days. Most employers round to half-days or full days. For PTO that accrues monthly, you'd earn 1.25 days per month worked (15 / 12).
How does pro rata work for dividends?
Dividends declared between record date and payment date are paid pro rata based on ownership. If you sold shares before the ex-dividend date, you don't receive the dividend. If you held through the record date, you get the full dividend per share regardless of how long you held the shares.
Is pro rata the same as proportional?
Yes, pro rata is just the Latin term for proportional distribution. Used in legal, financial, and HR contexts to express 'in proportion to time/share/usage.' Same calculation, more formal language.