Fidamen

Put Option Calculator

This calculator models standard put option scenarios: long put (buy), short put (sell), and an estimate of a synthetic put derived from put-call parity. Use the inputs to evaluate payoff at a chosen expiry price, breakeven, net profit/loss, and parity differences.

Designed for scenario analysis and educational insight. Results are deterministic algebraic computations based on your inputs; they do not incorporate real-time market execution, slippage, margin requirements, assignment probability, or tax effects.

Updated Nov 2, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 83917a784d7b • Reviewed by Fidamen Standards Committee

Standard long (buy) put position. Buyer pays premium and benefits when underlying falls below strike at expiry.

Inputs

Results

Updates as you type

Total premium paid

$250.00

Net cost (including fees)

$251.00

Payoff at expiry (before premium)

$0.00

Net profit at expiry

-$251.00

Breakeven price (per share)

$97.50

OutputValueUnit
Total premium paid$250.00USD
Net cost (including fees)$251.00USD
Payoff at expiry (before premium)$0.00USD
Net profit at expiry-$251.00USD
Breakeven price (per share)$97.50USD
Primary result$250.00

Visualization

Methodology

Payoff calculations compute per-share payoff at expiry then scale by number of contracts and contract size. Premiums are treated on a per-share basis and multiplied by contract quantity.

The synthetic put estimate uses put-call parity: P = C - S + K * e^{-rT}. Present value of strike is calculated with continuous discounting using the provided risk-free rate and time to expiry (days/365).

Data integrity and testing procedures follow best-practice principles for reproducible financial calculators. Development and testing recommendations align with NIST guidance on software testing and verification, ISO software quality management principles, and IEEE recommendations for numerical accuracy validation. Operational safety and workplace processes should follow applicable OSHA guidance where relevant.

Worked examples

Example 1: Long 1 put on 100 shares with strike 100, premium 2.50, fees 1. Payoff at expiry if underlying is 90: (100 - 90) * 100 = 1000; net profit = 1000 - (2.5*100) - 1 = 749.

Example 2: Short 2 puts on 100 shares with strike 50, premium 1.00, fees 2. If underlying is 40 at expiry, seller payoff = -(50 - 40) * 200 = -2000; net profit = (1.00*200 - 2) - 2000 = -1802.

F.A.Q.

How accurate are these calculations?

Calculations are algebraic and precise given the supplied inputs. They do not model execution risk, early assignment, margin, or path‑dependent payoffs. For model verification and numeric testing practices, follow NIST and IEEE testing recommendations. Use results as a scenario guide, not trading advice.

Does the tool price options (Black‑Scholes) or compute Greeks?

This tool focuses on payoff, breakeven, and parity comparisons. It does not compute Black‑Scholes theoretical prices or Greeks. Use a dedicated pricing model when you need implied volatility calibration or Greek sensitivities.

What assumptions underlie the synthetic put calculation?

Put-call parity assumes European-style options, frictionless markets, and the ability to borrow/lend at the risk-free rate. The synthetic expression uses continuous discounting of the strike price (K * e^{-rT}). Market realities like dividends, transaction costs, and early exercise for American options can create deviations.

How should I validate results before trading?

Cross-check with a regulated broker or exchange-provided calculators, perform sensitivity checks (vary premium, underlying, T), and document test cases. Follow ISO software quality and NIST recommended testing protocols for reproducibility. Maintain audit trails of input parameters and test results.

Sources & citations

Further resources

External guidance

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: 83917a784d7b

What changed (latest)

v1.0.0 • 2025-11-02 • 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 2, 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 • 2025-11-02 • 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: 15ae8cb64838