# What is the pro rata share?

Works out a pro rata share: an amount × part ÷ whole, such as a part-time salary or a bill for days used, or an amount split among several people in proportion to their shares.

- Page: https://www.acalculator.org/finance/pro-rata-calculator
- JSON spec: https://www.acalculator.org/finance/pro-rata-calculator.json
- Version: 8fdbafe4c4ff

## Default answer

Example with the default inputs (Work out One share, Full amount $60,000.00, Your part 24, The whole 40): The pro rata amount is $36,000.00 of $60,000.00.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| mode | Work out | One share of an amount, or the amount split among several parties. |
| amt | Full amount | The whole amount to share out: a full-time salary, a yearly bill, a dividend or a cost. |
| part | Your part | Your part of the whole, such as hours worked, days used or shares owned. |
| whole | The whole | The whole the full amount is for, in the same units as your part. |
| parties | Parties | Each party’s units: shares owned, days, hours or any measure of their part. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| share | Pro rata amount | Full amount × part ÷ whole (in a split, the first party’s amount). |
| percent | Share of the whole | Part ÷ whole × 100 (in a split, the first party’s share). |
| rest | Rest of the amount | Full amount minus the pro rata amount. |
| perUnit | Amount per unit | Full amount ÷ the whole (all units). |
| each | Each party | Each party’s share of the amount and percent, in the order typed. |
| summary | Answer | The answer in one sentence. |

## Method

Pro rata amount = full amount × part ÷ whole. In a split, each party gets full amount × its units ÷ all units.

## Assumptions

- The part and the whole are in the same units (hours, days, shares, square feet).
- A part larger than the whole gives more than the full amount, as with overtime.
- Amounts in the split list are rounded to the cent one by one, so they can differ from the full amount by a few cents in total.

## Worked examples

1. mode = share, amt = $60,000.00, part = 24, whole = 40 gives share = $36,000.00, percent = 60%, rest = $24,000.00, perUnit = $1,500.00. Source: IRS, Instructions for Form 1120-S, Shareholder’s Pro Rata Share Items, General Rule (each shareholder’s pro rata share is determined by the number of shares of stock owned each day and the total shares outstanding each day), https://www.irs.gov/instructions/i1120s (retrieved 2026-10-02).
2. mode = share, amt = $1,200.00, part = 73, whole = 365 gives share = $240.00, percent = 20%, summary = The pro rata amount is $240.00 of $1,200.00. Source: IRS, Instructions for Form 1120-S, Shareholder’s Pro Rata Share Items, General Rule (each shareholder’s pro rata share is determined by the number of shares of stock owned each day and the total shares outstanding each day), https://www.irs.gov/instructions/i1120s (retrieved 2026-10-02).
3. mode = split, amt = $10,000.00, parties = {"units":50} or {"units":30} gives share = $5,000.00, each = Party 1: $5,000.00 (50%); Party 2: $3,000.00 (30%); Party 3: $2,000.00 (20%). Source: IRS, Instructions for Form 1120-S, Shareholder’s Pro Rata Share Items, General Rule (each shareholder’s pro rata share is determined by the number of shares of stock owned each day and the total shares outstanding each day), https://www.irs.gov/instructions/i1120s (retrieved 2026-10-02).
4. mode = split, amt = $100.00, parties = {"units":1} or {"units":1} gives share = $33.33, each = Party 1: $33.33 (33.33%); Party 2: $33.33 (33.33%); Party 3: $33.33 (33.33%). Source: IRS, Instructions for Form 1120-S, Shareholder’s Pro Rata Share Items, General Rule (each shareholder’s pro rata share is determined by the number of shares of stock owned each day and the total shares outstanding each day), https://www.irs.gov/instructions/i1120s (retrieved 2026-10-02).

## FAQ

### What does pro rata mean?

"In proportion." A pro rata share is the part of an amount that matches your part of the whole: if you own 30 of 100 shares, you get 30% of a payout; if you use a service for 73 of 365 days, you pay 20% of the yearly fee.

### How do I calculate a pro rata amount?

Multiply the full amount by your part and divide by the whole: pro rata amount = amount × part ÷ whole. A $1,200 yearly bill for 73 days is 1,200 × 73 ÷ 365 = $240.

### How do I work out a pro rata salary?

Use hours (or days) as the part and the whole. A $60,000 full-time salary for 24 hours of a 40-hour week is 60,000 × 24 ÷ 40 = $36,000 a year, 60% of full time.

### How is income shared pro rata among S corporation shareholders?

The IRS instructions for Form 1120-S say each shareholder's pro rata share is based on the shares owned each day and the total shares outstanding each day. If the shares do not change during the year, that is simply each holder's shares ÷ all shares. With 50, 30 and 20 of 100 shares, $10,000 splits into $5,000, $3,000 and $2,000.

### Why do my split amounts not add up to the total?

Each amount is rounded to the cent on its own. $100 split three ways is $33.33 each, which adds to $99.99. Decide who gets the extra cent; the unrounded shares add up exactly.

### Is prorated rent the same thing?

It is one case of it: rent × days lived there ÷ days in the month. The prorated rent calculator handles the month lengths and move-in dates for you.

## Sources

- IRS, Instructions for Form 1120-S (2025), Schedules K and K-1, Shareholder’s Pro Rata Share Items, General Rule (each shareholder’s pro rata share of items is determined by the number of shares of stock owned each day during the tax year and the total number of shares outstanding each day). https://www.irs.gov/instructions/i1120s (retrieved 2026-10-02)