What is a stock option strike price?

The strike price (also called the exercise price) is the fixed dollar amount per share you pay to convert a stock option into an actual share. It's set once, at grant, based on the company's fair market value at that moment — and it never changes for the life of that grant, no matter how the stock's value moves afterward.

When Jordan joined a 40-person startup, her offer letter listed 15,000 options with a strike price of $1.10. Two years later, the company's internal valuation put the common stock at $6.40 a share. Jordan still only pays $1.10 to buy each share — that gap between what she pays and what the shares are actually worth is the entire point of holding options.

Key points

• The strike price is set at grant using the company's 409A valuation and is locked in for the life of the option — it does not move with the company's value.
• Strike price is not the same as exercise cost: exercise cost is strike price × number of shares, plus any taxes owed, which can be a much bigger number.
• You can find your strike price on your grant agreement, option/notice of grant document, or your company's cap table platform (Carta, Pulley, Shareworks, etc.).

How the strike price is set

Private companies can't just pick a strike price out of thin air. Under IRC Section 409A, the strike price for options on privately held stock generally must be set at or above the fair market value (FMV) of the common stock on the grant date, determined through an independent appraisal called a 409A valuation.

Here's the intuition for why this rule exists: the IRS wants to prevent companies from handing out options priced below real value as a way to disguise extra compensation and dodge taxes. A 409A valuation is the company's evidence that the strike price was set fairly, which protects both the company and the employee from penalty taxes.

A 409A valuation is generally valid for up to 12 months, or until a "material event" happens sooner — a new funding round, a major revenue shift, an acquisition offer. Whichever comes first resets the clock, and the company must get a fresh valuation before granting more options at a new price (see multiple industry 409A guides, e.g. AngelList's 409A explainer). That's why two people who join the same company eight months apart often have noticeably different strike prices — the underlying 409A valuation moved between their start dates, even though the company's actual value may have shifted continuously in between.

Why the strike price never changes

Once your grant is signed, the strike price is fixed for the entire life of that option — typically up to 10 years. This holds true even if:

• The company raises a new funding round at 5x the old valuation
• The stock price falls after a down round
• The company goes public and the stock trades wildly above or below your strike price

Think about it this way: the strike price is a promise baked into the contract on day one. It's precisely what makes options valuable when the company grows — you locked in yesterday's price for a share of tomorrow's company. It's also what makes options worthless (a plain "underwater" option) if the value falls below the strike price and stays there, since there's no reason to pay more than a share is worth.

The one exception worth knowing: some companies occasionally offer a formal repricing to employees when the stock has fallen significantly, lowering the strike price on existing grants going forward. This requires board approval and a new grant action — it isn't automatic, and most companies never do it.

Strike price vs. exercise cost

This is the single most common point of confusion, so it's worth separating clearly:

• Strike price is the price per share.
• Exercise cost is the total amount you actually pay to exercise, which is strike price × number of shares you're exercising — plus, often, taxes owed on the spread (for NSOs, always; for ISOs, potentially AMT). See our ISO vs NSO tax comparison for how that tax bill differs by option type.

A $1.10 strike price sounds tiny. But if you're exercising 15,000 shares, the exercise cost is $16,500 in cash before any tax is considered — and if it's an NSO with a large spread, the tax bill on top of that can dwarf the exercise cost itself. People regularly underestimate this because they anchor on the small per-share number instead of the total cash required.

Where to find your strike price

Your strike price is documented in a few predictable places:

• Your grant agreement / notice of stock option grant — the legal document you signed when the options were issued. This is the authoritative source.
• Your company's equity management platform — most companies now use a cap table tool like Carta, Pulley, or Shareworks where employees can log in and see strike price, vesting schedule, and grant date for every grant.
• Your offer letter, though this is sometimes an estimate pending final board approval — always confirm against the signed grant agreement.

If you have multiple grants from different years, expect multiple strike prices — one per grant, each reflecting the 409A valuation in effect when that specific grant was approved.

A worked example

Marcus was granted 8,000 options with a strike price of $0.85 when he joined a Series B startup. Eighteen months later, after a Series C round, the company's most recent 409A valuation set the common stock FMV at $4.20 per share.

• Strike price: $0.85/share (fixed, from his original grant — this does not change)
• Current FMV: $4.20/share (this moves with each new 409A)
• Spread per share: $4.20 − $0.85 = $3.35
• Total spread across the grant: $3.35 × 8,000 = $26,800
• Exercise cost (cash to exercise, before tax): $0.85 × 8,000 = $6,800

If these were NSOs, Marcus would owe ordinary income tax on the $26,800 spread at exercise, on top of the $6,800 exercise cost — meaning the actual cash required could easily be $15,000–$20,000 or more once withholding is included, depending on his tax bracket. If these were ISOs, he'd owe no regular tax at exercise, but the $26,800 spread would be an AMT preference item that could still generate a tax bill with no cash sale to fund it. Either way, the strike price itself — $0.85 — never moves. What changes is everything built on top of it.

The formula

Exercise cost = Strike price × Number of shares exercised

Spread (bargain element) = (Current FMV − Strike price) × Number of shares

Total cash needed to exercise ≈ Exercise cost + Taxes owed on the spread
  (taxes owed depends on ISO vs. NSO — see iso-vs-nso-tax-differences)

How WealthOS helps

Connect your grant agreements in WealthOS and we'll pull your exact strike price per grant, track the latest 409A FMV automatically, and show you the real total cash cost — exercise price plus estimated taxes — before you commit to exercising.

Related reading

• ISO vs. NSO: the tax differences that matter
• The $100k rule: how it splits your ISOs and NSOs
• When should you exercise your stock options?
• Should you exercise before an IPO?

Sources

• IRC Section 422 — Incentive Stock Options
• AngelList Education Center — What is a 409A Valuation?
• Morgan Stanley at Work — 409A Valuation FAQ and Guide

This article is educational and not tax, legal, or financial advice. Talk to a CPA or tax advisor about your specific situation.