Stock Basis Calculator
Estimate stock cost basis across purchase lots, dividend reinvestment, stock splits, and a possible sale. Use official brokerage and tax records for filing.
Purchase Lots
Lot 1
Lot 2
Adjustments
Use 1 for no split, 2 for a 2-for-1 split, or 0.5 for a 1-for-2 reverse split.
Direct answer
Stock basis starts with purchase cost, then changes for reinvested dividends and corporate actions. The current estimated total basis is $7,965.00, or $51.91 per split-adjusted share.
Cost Basis Summary
Shares after split
153.448
Total basis
$7,965.00
Basis per share
$51.91
Dividend shares
3.448
Sale Inputs
Capital Gain Estimate
Net sale proceeds
$5,240.00
FIFO gain or loss
$1,482.50
Basis sold: $3,757.50
Average-style gain or loss
$1,346.99
Basis sold: $3,893.01
Lot and Sale Basis Table
| Lot | Available shares | Shares used in sale | Basis used |
|---|---|---|---|
| 2023-01-15 | 100 | 75 | $3,757.50 |
| 2023-06-20 | 50 | 0 | $0.00 |
| Dividend reinvestment | 3.448 | 0 | $0.00 |
Formula Guide
| Item | Formula | Use for | Main caution |
|---|---|---|---|
| Purchase lot basis | (shares x price per share) + commission | Record the starting basis for each purchase | Fees, transfers, and corporate actions can require adjustments |
| Reinvested dividend shares | reinvested dividend amount / reinvestment price | Estimate new shares created by dividend reinvestment | Use actual reinvestment records when available |
| Split-adjusted shares | shares before split x split multiplier | Adjust share count after a split or reverse split | Total basis usually stays the same, while per-share basis changes |
| Capital gain or loss | net sale proceeds - basis of shares sold | Estimate gain or loss before tax forms | Wash sales, covered/noncovered status, and tax lots can change reporting |
Method and Worked Example
This worksheet adds purchase lot basis, adds reinvested dividend basis, adjusts shares for a split, then estimates gain or loss using net sale proceeds minus basis of shares sold.
Worked example: buying 100 shares at $50 with a $10 commission creates $5,010 of basis. If a later $200 dividend is reinvested, total basis increases by $200. A 2-for-1 split doubles share count but does not double total basis.
IRS Sources
Educational estimate only. Use your brokerage statements, Form 1099-B, Form 8949, Schedule D, and IRS guidance for actual filing. Corporate actions, wash sales, transfers, covered status, and tax-lot instructions can change reported basis.
FAQ
What is stock cost basis?
Stock cost basis is generally what you paid for shares plus purchase costs, adjusted for events such as reinvested dividends, stock splits, return of capital, wash sales, and transfers. It is used to estimate gain or loss when shares are sold.
How do reinvested dividends affect cost basis?
A reinvested dividend usually creates an additional purchase lot. The reinvested dividend amount increases total basis, and the new shares increase total shares owned.
How does a stock split affect basis?
A stock split normally changes the number of shares while total basis stays the same. Per-share basis is adjusted by spreading the same total basis over the new share count.
What method does this calculator use for a sale?
The main sale estimate uses FIFO, meaning oldest shares are treated as sold first. The page also shows an average-basis-style comparison for education, but actual tax treatment depends on security type, account records, and instructions to your broker.
Is this calculator tax advice?
No. This is an educational worksheet. It does not replace brokerage records, Form 1099-B, Form 8949, Schedule D, IRS guidance, or advice from a qualified tax professional.
About This Calculator
Calculate stock cost basis, adjusted shares after dividend reinvestment and splits, and estimated capital gain or loss. Educational tax worksheet only.
Frequently Asked Questions
What is stock cost basis?
Stock cost basis is generally what you paid for shares plus purchase costs, adjusted for events such as reinvested dividends, stock splits, return of capital, wash sales, and transfers. It is used to estimate gain or loss when shares are sold.
How do reinvested dividends affect cost basis?
A reinvested dividend usually creates an additional purchase lot. The reinvested dividend amount increases total basis, and the new shares increase total shares owned.
How does a stock split affect basis?
A stock split normally changes the number of shares while total basis stays the same. Per-share basis is adjusted by spreading the same total basis over the new share count.
What method does this calculator use for a sale?
The main sale estimate uses FIFO, meaning oldest shares are treated as sold first. The page also shows an average-basis-style comparison for education, but actual tax treatment depends on security type, account records, and instructions to your broker.
Is this calculator tax advice?
No. This is an educational worksheet. It does not replace brokerage records, Form 1099-B, Form 8949, Schedule D, IRS guidance, or advice from a qualified tax professional.
Alex specializes in personal finance modeling with experience in investment analysis and tax optimization. He reviews calculator logic, source notes, and assumptions so finance and tax pages explain their limits clearly.
- CFA Level II Candidate
- B.S. in Finance, University of Michigan
- 8 years in financial planning tools