Pro rata calculator

Pro rata rights let an investor put money into later rounds to keep their percentage. The amount is their share × the size of the new round.

The formula

Pro rata rights = share you own × size of the next round

Worked example: £200,000

The example uses the guide's seed round, £200,000 for 20%, with a matching cap table, exit, fund and market.

10.0% × £2,000,000 = £200,000 to keep your share

Try it with your numbers

Work out your pro rata rights

It starts on the example. Replace any figure with your own; nothing you type leaves your browser.

Your deal numbers

Start with any one figure. Each one you add works out more below. Your numbers are kept in this browser only.

What this calculation uses

Share you own now (needed)

Size of the next round (needed)

Its pre-money valuation

Add more of your numbers

Open a group to fill it in. Everything you add shows up in the list below the calculator.

An investment offer

Investment offered

For this share of the company

Your round

Pre-money valuation

You can type 2m or 750k.

New investment

Shares in issue

Options already granted

Unallocated option pool

In shares. 0 if you have none.

Option pool wanted after the round

Your own shares

Money converting at the round

Amount converting

From an ASA, SAFE or loan note.

Valuation cap

Leave blank for no cap.

Discount

Interest a year (loan notes)

Months since the note was issued

A sale of the company

Sale price of the company

What the preferred investor put in

What the preferred investor owns

1x2x

Participating preference

What the founders own

An investor's return

Amount invested

Share bought

Later dilution

30 means later rounds shrink that share by 30%.

Sale price at the exit

Years to the exit

The next round

Last round's post-money

New round's pre-money

A venture fund

Fund size (committed)

Paid in by investors so far

Invested in companies so far

Paid back to investors

Value of what the fund still holds

Your market

Potential customers

What one pays a year

Share you can serve

Share of those you could win

A SEIS, EIS or VCT investment

Amount an investor puts in

Shares that vest

Shares or options granted

Vesting period

Cliff

Months worked so far

Your pro rata amount

£200,000

10.0% × £2,000,000 = £200,000 to keep your share

Formula: Share you own × size of the next round.

Your share if you do not invest: 7.5%

How to read your result

An investor who skips their pro rata is diluted like everyone else. Founders should know who will take up their rights before the round.

Watch out for

Check whether the right covers the whole round or only part of it: some agreements cap it.

Last checked 24 October 2026. Estimates only, not financial, tax or legal advice: check your accounts and documents, and take advice before you act. More terms in the startup glossary.