Stock Split and Bonus Calculator

This stock split calculator estimates share count and theoretical price after a split, bonus issue or reverse split. For a valid split, shares multiply and price divides by the same factor. The form supports simple whole-number splits; general new-for-old ratios can give wrong results. Its Adjusted Cost Basis card uses your entered current price, so it cannot establish your original purchase cost. Check the ratio limits below before using the output.

More shares does not mean a larger investment

A split divides existing shares into smaller units. A bonus issue adds shares to the eligible holding. In a purely mechanical adjustment, the theoretical price changes in the opposite direction to share count. That arithmetic does not predict the price at which the stock will actually trade.

Read the company announcement to identify the action and its meaning before typing a ratio. A stock split and a bonus issue can lead to the same total quantity while describing different actions. A bonus ratio specifies extra shares; a split ratio specifies the replacement holding.

The ratio means something different in each mode

A general split of three new shares for two old shares needs a multiplier of 1.5. Typing 3:2 here instead uses a multiplier of 3. Do not use that output for your holding. The official NSE education material defines split adjustment as new shares divided by old shares; this form does not implement that general rule correctly.

For a reverse split, check whether the company expresses its ratio as old shares surrendered or new shares issued. The larger-number rule cannot interpret every announcement. Invalid or empty ratio text can silently become a preset ratio, while a zero share count or zero price can also use defaults. Re-enter valid inputs if a result looks unexpected.

What the four controls actually ask for

• Corporate Action chooses Stock Split, Bonus Issue or Reverse Split.
• Current Shares Held is the holding before the action. This calculator does not establish whether that holding qualifies for the event.
• Current Price per Share is the pre-action market price for a theoretical value comparison. It is not automatically your original purchase price.
• Split/Bonus Ratio is interpreted according to the selected action. There is no stock lookup, announcement date, purchase date or cash-for-fractions field.

Use figures from the same stage of the action. Entering a price already adjusted for the split alongside the old share count applies the adjustment again. Keep the company notice and broker statement beside the result so the quantity and price refer to the same event.

Worked split example: check both sides of the value

In this made-up example, select Stock Split, enter 120 shares, a current price of ₹600 and ratio 1:2. Assume an exact whole-share result with no other price movement. These are illustrative values for an unnamed company.

• Share multiplier: 2. New Total Shares: 120 × 2 = 240 shares.
• New Price (Est): ₹600 ÷ 2 = ₹300.
• Additional Shares: 240 − 120 = 120 shares.
• Value Before: 120 × ₹600 = ₹72,000. Value After: 240 × ₹300 = ₹72,000.
• Price Reduction: (600 − 300) ÷ 600 × 100 = 50%. Adjusted Cost Basis card: 72,000 ÷ 240 = ₹300.

The result shows how the same assumed holding value is spread over more shares. The price reduction is not an investment loss by itself. Compare total value with total value, using a consistent price basis, rather than comparing only the old and new per-share figures.

Bonus and reverse-split examples

For a separate illustrative bonus, assume 80 existing shares at ₹900 and a 1:1 bonus. Extra shares are 80 × 1 ÷ 1 = 80; the total is 160. Theoretical price is (80 × 900) ÷ 160 = ₹450. Both theoretical holding values are ₹72,000. The tool spreads that value across the total quantity; it has not determined the tax treatment of either share batch.

For an illustrative reverse split, assume 105 shares at ₹40 and ratio 5:1. The exact entitlement would be 21 shares, and this form returns 21. The estimated price is 40 × 5 = ₹200; the value remains 21 × 200 = ₹4,200. This example deliberately divides evenly.

When a reverse split does not divide evenly, the tool keeps only whole shares and can show a lower Value After without calculating the missing fractional entitlement. Check the issuer’s stated treatment. Do not assume the difference is a market loss or an established cash payment.

The cost-basis and commentary cards need care

Adjusted Cost Basis divides the value calculated from Current Price per Share by New Total Shares. Because there is no purchase-cost input, the result cannot reconstruct what you paid. For tax reporting, preserve original purchase records and the action documents, and ask a tax adviser how the actual share batches should be recorded.

Liquidity Impact and Trading Tip are preset comments attached to price levels and action type. They do not measure trading volume, available orders or business quality. Tax Impact is also generic wording; it does not review your acquisition history, residency, sale or company terms. The numerical share calculation cannot validate those comments.

If you are reviewing overall holdings, use the portfolio risk calculator with its own stated limits. To plan the quantity in a separate cash-share trade, see the stock position size calculator. Neither action automatically calls for a new trade.

Split and bonus questions

Sources

• NSE: corporate action adjustment examples, checked 16 Oct 2026.