Stock Split Calculator
This calculator converts a forward or reverse stock split ratio into the expected post-split share count and share price for a given holding, and computes theoretical market capitalization and percent price change. It is intended for planning and illustrative purposes.
The tool supports any split described as a ratio (numerator:denominator). For example, a 1-for-5 reverse split is numerator 1 and denominator 5; a 2-for-1 forward split is numerator 2 and denominator 1.
Governance
Record 4014fa4f9ac8 • Reviewed by Fidamen Standards Committee
Inputs
Results
Post-split shares
200
Post-split price
$50.00
Market capitalization (theoretical)
$10,000.00
Price change (%)
400.00%
Change in share count
-800
| Output | Value | Unit |
|---|---|---|
| Post-split shares | 200 | — |
| Post-split price | $50.00 | USD |
| Market capitalization (theoretical) | $10,000.00 | USD |
| Price change (%) | 400.00% | — |
| Change in share count | -800 | — |
Visualization
Methodology
The calculator applies basic conservation of market value: a split changes the number of outstanding shares and the price per share inversely so that, in theory, market capitalization remains unchanged.
Inputs are multiplied or divided by the split ratio to produce post-split values. The calculator does not model market reactions, trading spreads, or corporate actions beyond the arithmetic split.
Rounding and fractional-share handling vary by broker and by exchange rules. Where brokers issue cash-in-lieu or round fractional shares, the real delivered position can differ from the pure arithmetic result; see the FAQs and citations for operational guidance.
Key takeaways
This calculator provides theoretical post-split share counts and prices using arithmetic rules. It is not a trade order tool and does not execute trades.
Verify fractional-share settlement, rounding, and tax treatment with your broker or tax advisor before relying on settlement outcomes.
Worked examples
Example 1: You own 1,000 shares at $10. A 1-for-5 reverse split (numerator=1, denominator=5) results in 200 shares at $50 (market cap remains $10,000).
Example 2: You own 100 shares at $2. A 2-for-1 forward split (numerator=2, denominator=1) results in 200 shares at $1 (market cap remains $200).
F.A.Q.
Does a stock split change the total value of my holdings?
In theory no: market capitalization equals shares × price and remains the same immediately after a purely arithmetic split. However, market reactions and brokerage rounding can create small differences in realized value.
How are fractional shares handled after a split?
Brokers and custodians handle fractional shares differently: some issue cash-in-lieu, some round to whole shares, and some allow fractional share ownership. Use the rounding policy selector to model common outcomes, and check your broker's published policies for final settlement rules.
Does this calculator account for taxes or market movement?
No. This tool models only the arithmetic effect of the split. It does not estimate capital gains, tax treatment, or subsequent market price movement.
Is the result exact for corporate reporting?
The output is a mathematical estimate. Official reporting and broker account statements may include adjustments, withholding, or rounding as required by corporate action agents or exchange rules; always confirm with official notices from the issuer or registry.
Sources & citations
- National Institute of Standards and Technology (NIST) - Risk Management and Data Integrity principles — https://www.nist.gov
- International Organization for Standardization (ISO) - Risk and quality management standards — https://www.iso.org
- IEEE Standards Association - best practices for numeric accuracy and validation — https://standards.ieee.org
- Occupational Safety and Health Administration (OSHA) - operational safety and process controls (relevant for implementation standards) — https://www.osha.gov
- U.S. Securities and Exchange Commission - Corporate actions and investor bulletins — https://www.sec.gov
- SEC — Investor.gov Educational Resources — https://www.investor.gov/
- CFA Institute — Global Investment Performance Standards (GIPS) — https://rpc.cfainstitute.org/gips-standards
- FINRA — Investment Products — https://www.finra.org/investors/investing/investment-products
Further resources
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
Record ID: 4014fa4f9ac8What changed (latest)
v1.0.0 • 2025-11-30 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
What changed (latest)
v1.0.0 • 2025-11-30 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Engine
v1.0.0
Data
Baseline (no external datasets)
Content
v1.0.0
UI
v1.0.0
Governance
Last updated: Nov 30, 2025
Reviewed by: Fidamen Standards Committee (Review board)
Credentials: Internal QA
Risk level: low
Reviewer profile (entity)
Fidamen Standards Committee
Review board
Internal QA
Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person
Semantic versioning
- MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
- MINOR: New features or fields that do not change existing outputs for the same inputs.
- PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.
Review protocol
- Verify formulas and unit definitions against primary standards or datasets.
- Run golden-case regression suite and edge-case suite.
- Record reviewer sign-off with credentials and scope.
- Document assumptions, limitations, and jurisdiction applicability.
Assumptions & limitations
- Uses exact unit definitions from the Fidamen conversion library.
- Internal calculations use double precision; display rounding follows the unit's configured decimal places.
- Not a substitute for calibrated instruments in regulated contexts.
- Jurisdiction-specific rules may require official guidance.
Change log
v1.0.0 • 2025-11-30 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: cfe6173d776b