Quick answer
How do you adjust stock inputs for a split?
For an A-for-B split, multiply each share quantity by A / B and divide each per-share price by A / B. Keep entered commission amounts unchanged. Apply the same ratio to every relevant purchase and sale quantity.
- 1
Enter old shares. The first field is the pre-split side of the announced ratio.
- 2
Enter new shares. A 1-to-2 ratio represents a 2-for-1 forward stock split.
- 3
Apply the split. The calculator scales every relevant share quantity and per-share price together.
- 4
Check the confirmation. The message verifies that position value and entered commissions remain unchanged.
2-for-1 example
100 shares at $50 become 200 shares at $25
Assume a purchase of 100 shares at $50 with a $10 Buy commission, followed by a 2-for-1 split.
Convert the split
2-for-1 means a ratio of 2.
Multiply quantity
100 x 2 = 200 shares.
Divide per-share price
$50 / 2 = $25 per share.
Verify purchase value
200 x $25 = $5,000, unchanged.
Keep the entered fee
The $10 Buy commission remains $10.
Verify total cost basis
$5,000 + $10 = $5,010, unchanged.
Post-split sale
A sale at $30 produces $980 in net profit
Sell 200 adjusted shares at $30 and pay a $10 Sell commission. Net proceeds are $5,990 and Net profit is $980 on the preserved $5,010 cost basis.
- Adjusted shares
- 200
- Adjusted buy price
- $25.00
- Sell price
- $30.00
- Net profit
- $980.00
- ROI
- 19.56%
Reverse ratio
A 1-for-5 reverse split divides shares and multiplies price
For a 1-for-5 reverse split, the ratio is 1 / 5, or 0.2.
Five hundred shares at $8 become 100 shares at $40. Both versions have a purchase value of $4,000 before commissions. The calculator supports fractional quantities, but real corporate actions may include cash in lieu of fractional shares that is outside this normalization workflow.
Position-wide consistency
Adjust every purchase and sale in the position
Purchase lots
Scale each lot's share quantity and per-share purchase price by the same ratio.
Previous sales
Scale historical sale quantities and per-share prices so remaining inventory stays consistent.
Current sale
Scale the current Shares sold and Sell price per share before comparing it with the adjusted lots.
Commissions
Preserve the entered dollar or percentage commission settings; do not scale a recorded flat fee.
For a combined position summary after normalization, see How to Calculate Average Stock Cost Basis.
Important limitation
Split normalization is not complete corporate-action accounting
The calculator handles the direct share-and-price scaling needed for its profit model.
Value check
Shares x per-share price should remain the same immediately before and after normalization.
Lot check
Shares and prices must be scaled within each purchase lot rather than only in the position total.
Excluded events
Mergers, spin-offs, return of capital, and cash paid for fractional shares can require additional basis adjustments.
Record check
Use issuer notices and brokerage records for an actual split and any associated basis reporting.
Methodology and references
Verify the split ratio and adjusted basis records
The calculator preserves modeled position value and entered commissions. Official issuer and brokerage records remain the source of truth for the actual corporate action.
Ready to normalize a position after a stock split?
Use the Stock Profit Calculator