About the Pro Rata Calculator
Pro rata means in proportion. When you move in halfway through a month, cancel a subscription early or start a job in the middle of a pay period, you pay or earn only for the days that apply. This calculator takes the full price, the dates the billing period runs and the dates you actually use it, then counts the days and gives the charge. It also shows the share of the period, the cost of one day and the amount left over, which is what you would be refunded. Both the first and the last day are counted. Nothing leaves your browser.
Updated October 2026
How to use the Pro Rata Calculator
- 1Enter the full price for the whole billing period.
- 2Choose the first and last day of the billing period.
- 3Choose the first and last day you use or work.
- 4Read the pro rata charge and the number of days.
- 5Use the leftover amount as the refund or unused portion.
Where pro rata comes up
Rent is the most common case. A tenant who takes over a flat on the 11th owes only the rest of that month, and a tenant who leaves early may be refunded the days unused. Software and gym subscriptions work the same way when you upgrade, downgrade or cancel in the middle of a cycle.
Salary and wages are prorated when someone starts or leaves in the middle of a pay period, and insurance, utilities and service fees often follow the same rule. The key is to agree up front whether days are counted as calendar days, working days or a 30 day month.
Checking the maths yourself
- Daily rate = full price divided by days in the period.
- Charge = daily rate multiplied by days used.
- Refund = full price minus the charge.
- Count both the start day and the end day, unless your agreement says otherwise.
- Round to the nearest cent only at the end.
Related tools
To count the days between two dates, use the Days Between Dates calculator and for business days use the Working Days Calculator. For a full year salary figure, the Salary Calculator converts between yearly, monthly and hourly pay, and the Hourly Rate Calculator helps with rates by the hour. These results are estimates for planning, and your contract decides the final amount.
Features
- Counts calendar days, both ends included
- Charge, share of period and cost per day
- Shows the unused or refundable amount
- Handles months of any length and leap years
- Clear error when your dates are outside the period
- Works for rent, subscriptions, salary and fees
- Private and free
Frequently asked questions
What does pro rata mean?
It is Latin for in proportion. A pro rata amount is a share of the full amount that matches the part of the period that applies.
How is the charge calculated?
It is the full price divided by the number of days in the period, multiplied by the number of days you use. For a 30 day month at 300, each day costs 10.
Are the first and last days counted?
Yes, both are counted. If you move in on the 11th of a 30 day month and stay until the 30th, you pay for 20 days.
Do I use calendar days or a 30 day month?
This page uses real calendar days. Some landlords or payroll systems use a flat 30 day month or a yearly rate divided by 365. Ask which rule your contract follows.
Can I use it for salary?
Yes. Use the pay period as the billing period and the days worked as your usage. Note that some employers prorate by working days instead of calendar days.
How do I work out a refund?
Enter the days you actually used. The leftover amount shown is the price for the days you did not use.
Why does it say my dates are outside the period?
Your usage dates must overlap the billing period, because there is no charge for days that fall outside it.