# Pro-rata calculator: how to work out rent, salary or fees for part of a month or year

> When someone joins, leaves or moves out in the middle of a period, the full amount has to be split fairly. This guide shows how pro-rata works, how the choice of days in the month changes the result, and where it is used for rent, pay and subscriptions.

Published 2026-10-09 by Toolcloak. 3 minute read. Original: https://toolcloak.pages.dev/articles/pro-rata-calculator-how-to-work-out-rent-salary-or-fees-for-part-of-a-month-or-year
Related free tool: [Pro-Rata Calculator](https://toolcloak.pages.dev/tools/pro-rata-calculator)

**Pro rata** means in proportion. If you pay for a whole month but use only part of it, you pay the same share of the amount as the share of the month you use. The method is the same for rent, salary, a gym fee or a software plan: find the amount for one day, then multiply by the days that count.

> **In short**
> - **Pro-rated amount = full amount × days charged ÷ days in the full period.**
> - A full amount of **₹30,000** for **12 days out of 30** is **₹12,000**. That is 40% of the period, at ₹1,000 a day.
> - The remaining amount is ₹18,000.
> - The number of days you divide by is a **choice** that the contract should state. Different choices give different amounts.

## The formula, step by step

**Example: ₹30,000 a month, 12 days charged**

1. **Find the daily amount.** ₹30,000 ÷ 30 days = **₹1,000** a day.
2. **Multiply by the days charged.** ₹1,000 × 12 = **₹12,000**.
3. **Find the share of the period.** 12 ÷ 30 = **40%**.
4. **Find what is left.** ₹30,000 − ₹12,000 = **₹18,000**.

*The tool shows the pro-rated amount, the amount per day, the remaining amount and the share of the period.*

Try it: [Pro-Rata Calculator](https://toolcloak.pages.dev/tools/pro-rata-calculator). Enter the full amount, the days in the full period and the days to charge to get the pro-rated amount.

## How much for different numbers of days

| Days charged (out of 30) | Pro-rated amount | Share of the period |
| --- | --- | --- |
| 5 | ₹5,000 | 16.7% |
| 10 | ₹10,000 | 33.3% |
| 12 | ₹12,000 | 40.0% |
| 15 | ₹15,000 | 50.0% |
| 20 | ₹20,000 | 66.7% |
| 25 | ₹25,000 | 83.3% |

*Same ₹30,000 and a 30-day period. The amount grows in a straight line with the days.*

**Pro-rated amount by days charged (₹)**

|  | Amount |
| --- | --- |
| 5 days | ₹5,000 |
| 10 days | ₹10,000 |
| 15 days | ₹15,000 |
| 20 days | ₹20,000 |
| 25 days | ₹25,000 |

*Each day adds ₹1,000 here. Halving the days halves the amount.*

## The hidden choice: how many days in the period?

A month has 28 to 31 days, and a contract may say to use the real number of days, or a fixed 30, or even the working days. The same ₹30,000 and 12 days give different amounts:

| Days used as the divisor | Amount per day | Amount for 12 days |
| --- | --- | --- |
| 28 days | ₹1,071.43 | ₹12,857.14 |
| 30 days | ₹1,000.00 | ₹12,000.00 |
| 31 days | ₹967.74 | ₹11,612.90 |

*The difference between 28 and 31 days is ₹1,244.24 for the same 12 days. Neither is wrong. The agreement decides.*

> **Agree the method first:** For rent, notice pay or final salary, write down whether you use the actual days in the month, a fixed 30 days or working days. It stops an argument over a few hundred rupees later.

## Where pro rata is used

- **Rent and deposits,** when a tenant moves in or out mid-month.
- **Salary,** for a joiner or leaver who works part of a month.
- **Subscriptions and memberships,** for a plan started or cancelled partway through.
- **Fees and insurance,** where cover or a service covers only part of a term.
- **Annual amounts,** such as a yearly plan used for a number of days.

**Two ways to use the same tool**

| Part of a month | Part of a year |
| --- | --- |
| ₹12,000 | ₹3,287.67 |
| ₹30,000 for 12 of 30 days | ₹12,000 plan used for 100 of 365 days |
| Joiner, leaver or tenant | Set the period to 365 days |
| Per day: ₹1,000 | Per day: ₹32.88 |

*The calculator does not care about the length of the period. Enter the days of the full period, whether 30, 31 or 365.*

**The example month in four numbers**

|  | Value | Note |
| --- | --- | --- |
| Pro-rated amount | ₹12,000 | 12 of 30 days |
| Per day | ₹1,000 | ₹30,000 ÷ 30 |
| Remaining amount | ₹18,000 | The unused part |
| Share of period | 40% | 12 ÷ 30 |

*The pro-rated amount and the remaining amount always add up to the full amount.*

## A short routine

1. **Write down the full amount** and the length of the full period in days.
2. **Count the days to be charged,** and decide whether the first and last days count.
3. **Agree the divisor** (actual days, 30 or working days).
4. **Run the calculator** and check that the amount and the remainder add up.
5. **Round to the nearest rupee** only at the end.

## Frequently asked questions

### How do I calculate pro-rata pay?

Divide the full amount by the number of days in the full period, then multiply by the days to be paid. For 30,000 a month and 12 days out of 30, it is 30,000 ÷ 30 × 12 = 12,000.

### Should I divide by 30 or the real days of the month?

It depends on your contract or policy. The real days give a slightly different amount in months of 28, 29 or 31 days. Agree the method first.

### How do I pro-rate an annual amount?

Enter the annual amount, 365 days (or 366 in a leap year) as the full period, and the days to charge. A 12,000 plan used for 100 days comes to about 3,287.67.

### What does the remaining amount mean?

It is the part of the full amount for the days that are not charged. With 30,000 and 12 days charged out of 30, the remaining amount is 18,000.

### Can days to charge be more than the full period?

No. The tool asks for a number between 0 and the length of the full period.

### Is the pro-rata amount the same as a refund?

Not always. A refund may also include fees or a minimum charge. For a daily figure alone, you can also use the [Time Calculator](https://toolcloak.pages.dev/tools/time-calculator) or the [Date Difference Calculator](https://toolcloak.pages.dev/tools/date-difference-calculator) to count the days.