Stock Split Calculator

Adjust share count and cost basis for a forward or reverse split, including the cash paid for fractional shares.

A share split hands out new certificates for the same ownership. The company is worth what it was worth a second earlier, the holder owns the same fraction of it, and the only things that changed are how many pieces that fraction has been divided into and the price marked on each piece. Everything a stock split calculator does follows from taking that sentence literally.

Formula: new shares = old shares x ratio; basis per share = old basis per share / ratio

Your figures

Currency

Number of shares

Held immediately before the split.

Share price

The price per share before the split takes effect. The adjusted price is derived from it.

Cost basis

What the shares cost, read according to the setting beside it.

Cost basis entered as

Whichever figure you have to hand. The total is what the split leaves untouched, so a per-share basis is multiplied by the share count before anything else happens.

Split ratio — new shares

The first number an announcement quotes. A 3-for-2 forward split is 3 here; a 1-for-10 reverse split is 1.

Split ratio — old shares

The second number. A 3-for-2 forward split is 2 here; a 1-for-10 reverse split is 10.

Cash paid for the fraction

Whether the registrar pays out an entitlement below one whole share instead of carrying it. Registrars that support fractional positions simply hold it.

Results

Shares after the split

262

3-for-2 · US$64.00 a share · US$28.3333 of basis

Split ratioA forward split: more shares, each at a proportionately lower price.: 3-for-2 · 1.500000x
Shares before: 175
Share entitlementShares held multiplied by the ratio, before any fractional handling.: 262.5
Whole shares: 262
Fractional entitlementThe part of the entitlement below one whole share. This is the only place real value moves in a split.: 0.5
Share price before: US$96.00
Split-adjusted priceThe price divided by the ratio. Applying the same division to every earlier price is what makes a chart comparable across the event.: US$64.00
Total cost basisIdentical before and after. A split hands out new certificates for the same ownership and changes nothing that was paid, so it is the basis per share that divides and never the total.: US$7,437.50
Cost basis per share before: US$42.5000
Cost basis per share afterThe unchanged total spread across the full entitlement, fraction included.: US$28.3333
Cash in lieu of the fractionThe fractional entitlement valued at the split-adjusted price.: US$32.00
Cost basis attached to the fractionThe fraction's share of the total basis, which leaves the holding with it.: US$14.1667
Gain on the cash paymentThe cash received less the basis that went with it. Small, and a disposal all the same.: US$17.83
Cost basis retainedThe total basis less the part that left with the fraction.: US$7,423.33
Shares after: 262
Position value before: US$16,800.00
Position value afterShares held at the adjusted price, plus any cash received. Equal to the value before, which is the check any split arithmetic has to pass.: US$16,800.00

What this means

A 3-for-2 split turns 175 shares into an entitlement of 262.5 and restates the price of US$96.00 as US$64.00, that price divided by the same ratio. The entitlement includes 0.5 of a share, which is paid out as US$32.00 at the adjusted price. That payment is a disposal: it carries US$14.1667 of basis with it, leaving US$17.83 of realised gain or loss and US$7,423.33 of basis on the shares still held. The total cost basis is US$7,437.50 both before and after, because nothing was bought or sold; what divides is the basis per share, from US$42.5000 to US$28.3333. Shares multiplied by price comes to US$16,800.00 on either side of the event, which is the arithmetic check a split has to satisfy.

Every figure above is yours to enter. No price, share count, earnings figure or commission is fetched from anywhere, and no broker's commission is preset — where a field opens with one it is a round illustration. That is what lets these work on a private company, a delisted one, a statement you would rather check than trust, and a date no live feed still serves.
No tax is computed. Which matching method a holder may use, whether a disposal is taxable at all, and how a payment for a fraction is characterised are questions of jurisdiction and of the individual holder's circumstances rather than of arithmetic.
A split is a relabelling. The company is worth what it was worth a second earlier and the holder owns the same share of it; only the number of certificates and the price on each have changed.
Dividing the total cost basis by the ratio alongside the share count is the common error and it is expensive: it halves the recorded cost of a holding in a 2-for-1 split and invents a gain that never occurred.
Whether a fraction is cashed out or carried depends on the registrar and on the account. Both are ordinary; the setting above asks rather than assumes.
Assumes the price and cost basis are in the currency selected above.

The link reopens this calculator with the same numbers. Nothing you enter is sent to a server.

Continue with these figures

About the Stock Split calculation

This one takes the shares held, the price, the cost basis — entered per share or for the whole holding, whichever figure you have — and the ratio as the announcement quotes it, with the first number the new shares and the second the old. Enter a ratio below one and the same page works as a reverse split calculator, with no mode to switch. It returns the entitlement, the whole shares and the fraction, the split-adjusted price, the basis per share before and after, and, when the registrar cashes out the fraction, the small disposal that payment represents.

Two identities have to survive the event, and they are the right way to check any split arithmetic against any source. Shares multiplied by price is the same before and after; total cost basis is the same before and after. The second is where share split cost basis is most often mishandled, because dividing the total basis by the ratio alongside the share count looks natural, halves the recorded cost of a holding in a two-for-one split, and invents a gain that never occurred.

Stock Split formula

ratio           = new shares ÷ old shares
entitlement     = shares held × ratio
adjusted price  = price ÷ ratio

total basis     = unchanged by the split
basis / share   = total basis ÷ entitlement

if the fraction is cashed out:
  fraction      = entitlement − floor(entitlement)
  cash in lieu  = fraction × adjusted price
  basis on it   = fraction × basis / share
  gain on it    = cash in lieu − basis on it

check:  shares × price is equal on both sides
        shares held after × adjusted price + cash = shares before × price

ratio: Above 1 for a forward split, below 1 for a reverse. A 3-for-2 is 1.5; a 1-for-10 reverse split is 0.1.
entitlement: The exact share count the ratio produces, before any fraction is dealt with. It can be fractional even when the holding was a whole number.
adjusted price: The price divided by the ratio. Applying the same division to every earlier price is what makes a chart comparable across the event.
cash in lieu: A payment made by the registrar instead of issuing part of a share. It is a disposal of that fraction, not a dividend.
floor: Round down to the whole number below. The fraction is what is left over, and it is the only place in a split where value genuinely moves.

The ratio is the single quantity everything else is built from, and reading it the wrong way round is the most common entry error. An announcement of a 3-for-2 split means three new shares for every two old ones, so the ratio is 1.5 and the holding grows; a 1-for-10 reverse split means one new share for every ten old ones, so the ratio is 0.1 and the holding shrinks by nine tenths while the price rises tenfold. The two boxes on this page keep the announcement's own wording rather than asking you to convert it first.

Total cost basis does not appear on the right-hand side of any split formula, and that absence is deliberate. A split involves no purchase, no sale and no payment, so nothing about what the holding cost has changed; what changes is only how that unchanged sum is spread. Dividing the total by the ratio as well as the share count is the error the identity above catches: the check that shares multiplied by price is equal on both sides will still pass while the basis is quietly wrong, which is exactly why the basis needs a check of its own.

The split-adjusted price is why historic charts do not show a cliff on the split date, and restating those prices is the whole of what a split adjusted price calculator does. Every price before the event is divided by the same ratio, so a series recorded across a two-for-one split reads continuously rather than appearing to halve overnight. It also means a price quoted from before a split and compared with one from after it is not comparing anything: one of the two has to be restated first, and this is the arithmetic that restates it.

The fraction is the one place real value moves, and the calculator treats it as the small disposal it is. A holder of 175 shares through a 3-for-2 split is entitled to 262.5 shares, and a registrar that does not carry fractional positions pays out the half. That payment carries half a share's worth of basis with it, and the difference between the cash and that basis is a realised gain or loss — usually trivial in size, and a disposal all the same. Registrars that support fractional holdings simply carry the 0.5, which is why the setting asks rather than assumes.

Stock Split: a worked example

A holding of 175 shares priced at 96.00, with a cost basis of 42.50 a share, going through a 3-for-2 forward split where the registrar pays cash for any fraction rather than carrying it.

Ratio3 ÷ 2 = 1.5
Entitlement175 × 1.5 = 262.5 shares — 262 whole and a fraction of 0.5
Adjusted price96.00 ÷ 1.5 = 64.00
Total cost basis175 × 42.50 = 7,437.50, before and after alike
Basis per share after7,437.50 ÷ 262.5 = 28.3333, which is 42.50 ÷ 1.5
Cash for the fraction0.5 × 64.00 = 32.00
Basis leaving with it0.5 × 28.3333 = 14.17, so the gain on the payment is 32.00 − 14.17 = 17.83
Position value check175 × 96.00 = 16,800 before; 262 × 64.00 + 32.00 = 16,800 after

262 shares at 64.00 plus 32.00 in cash, against 175 shares at 96.00 — the same 16,800 on both sides, which is the check the arithmetic has to pass. The basis per share fell from 42.50 to 28.3333 while the total held at 7,437.50, less the 14.17 that went out with the fraction. Had the total basis been divided by 1.5 alongside the share count, the recorded cost would have fallen to 4,958.33 and a gain of nearly 2,500 would have been invented out of an event in which nothing was bought or sold.

How to use the Stock Split calculator

Enter the ratio exactly as the announcement words it. The first box is the new shares and the second is the old, so a 3-for-2 is 3 and 2, and a 1-for-10 reverse split is 1 and 10.
Put in the share count and price as they stood immediately before the split takes effect. The adjusted price is derived from the pre-split price rather than being asked for separately, so there is no second figure to keep consistent.
Choose whether the cost basis you have is per share or for the whole holding, then enter that figure. The total is the anchor everything else is derived from, so a per-share figure is multiplied up before anything happens to it.
Set the fractional share cash-in-lieu switch to match your registrar. Both behaviours are ordinary — many now carry fractional positions and simply hold the remainder — and the difference shows up as a small realised gain or loss rather than as a change in the share count alone.
Use the split-adjusted price to restate earlier prices in your own records. Every price from before the event divides by the same ratio, which is what makes a chart or a spreadsheet continuous across the date.
Carry the adjusted share count and basis per share into the cost basis calculator if you are then working out a gain, since a split is not a transaction and has no row of its own there.

Limitations of the Stock Split calculator

Every calculation makes assumptions. These are the ones that matter here.

Applies one split to one holding. A sequence of splits has to be run through in order, using each result as the input to the next, because the ratios compound rather than add.
Says nothing about the tax treatment of a cash-in-lieu payment. Whether it is a disposal, how any gain on it is characterised, and whether it falls under a small-payment simplification all depend on jurisdiction and circumstances.
Covers only splits and consolidations. A spin-off, a rights issue, a scrip dividend or a return of capital also changes the share count or the basis, and each of those apportions value differently from a split.
Assumes the registrar values a cashed-out fraction at the split-adjusted price entered here. In practice the payment is usually based on the actual traded price on a particular day, which will differ, and the gain on that fraction moves with it.
Takes the price as one figure rather than a market. Around a split announcement the price moves for reasons unrelated to the arithmetic, and this calculator restates a number rather than explaining why it changed.
Assumes the price and the cost basis are in the same currency, with no conversion applied to either.

Frequently asked questions about Stock Split

Does a stock split make a holding more valuable?

No. The holder ends up with more shares, each worth proportionately less, and the position value identity above holds exactly: 175 shares at 96.00 and 262.5 shares at 64.00 are both 16,800. What a split changes is the size of the unit — a lower price per share can widen the pool of buyers able to deal in round amounts — but the arithmetic itself moves nothing.

Why does the total cost basis stay the same when the share count goes up?

Because cost basis records what was actually paid, and a split involves no payment. Nothing was bought, nothing was sold, and no money changed hands, so the total is untouched and only its distribution across a larger number of shares changes. Dividing the total by the ratio would restate history as though the holding had been bought more cheaply than it was.

How do I adjust prices from before a split?

Divide every one of them by the same ratio, which is what the split-adjusted price on this page does to the current price. A 2-for-1 split makes every pre-split price half of what it was recorded as, so a chart reads continuously across the date and a comparison between a pre-split price and a post-split price is measuring the same thing.

What happens to the fractional share?

It depends on the registrar. Some carry fractional positions and simply hold it, in which case nothing leaves the holding and the whole basis stays with it. Others pay cash instead, which is a disposal of that fraction: the payment carries the fraction's share of the basis with it, and the difference between the two is a small realised gain or loss.

Does a reverse split calculator need the ratio entered the other way round?

No — the ratio boxes take the announcement's own wording either way. A 1-for-10 reverse split is 1 in the new-shares box and 10 in the old, which gives a ratio of 0.1, ten times the price per share and a tenth of the count. Reverse splits produce fractions far more often than forward ones, because most holdings are not exact multiples of ten or twenty.

Why did my broker's share count differ from the entitlement shown?

Almost always because of the fraction. If the entitlement is 262.5 and the registrar does not carry fractions, the account shows 262 shares and a small cash credit; if it does carry them, it shows 262.5. Rounding conventions also vary between registrars for the payment itself, which is why the cash figure here is an estimate at the adjusted price rather than the exact amount received.

Last reviewed 29 August 2026. See our methodology and editorial policy.

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