Four inputs, two steps, one number. The formula is simpler than the equity-portal dashboard suggests — and learning it once means you can sanity-check Carta, model a job change, or decide whether to wait a month before quitting.
Pull these four numbers from your grant. They're on the first or second page of the option agreement and mirrored in your equity portal.
The first case is the most common — 4-year vesting with a 1-year cliff, monthly post-cliff.
Before the cliff date
Vested = 0
On or after the cliff date
Vested = (Total ÷ 4) + (months since cliff × Total ÷ 48)
For quarterly post-cliff vesting, swap the second term: each completed quarter past the cliff adds (Total ÷ 16) shares.
Quarterly post-cliff
Vested = (Total ÷ 4) + (quarters since cliff × Total ÷ 16)
Imagine a 10,000-share grant. Grant date is January 15, 2025. Standard 4-year schedule, 1-year cliff, monthly vesting after. You want to know how many shares are vested as of November 1, 2026.
Grant date + 12 months = January 15, 2026. Before that date, 0 vested.
On January 15, 2026, 2,500 shares vest. (10,000 ÷ 4 = 2,500.)
January 15, 2026 to November 1, 2026 is roughly 9 full months. Since most schedules vest on the 15th of each month, count complete monthly anniversaries: Feb 15, Mar 15, Apr 15, May 15, Jun 15, Jul 15, Aug 15, Sep 15, Oct 15. That's 9 monthly vest events.
Each monthly tranche is 10,000 ÷ 48 ≈ 208.33 shares. Companies typically round; let's call it 208 per month. 9 × 208 = 1,872 shares.
Total vested as of November 1, 2026: 2,500 + 1,872 = 4,372 shares. Roughly 44% of the grant.
Your equity portal — Carta, Shareworks, Pulley, AngelList Stack, Solium, Equity Edge — shows your vested count daily. Compare your hand calculation to what the portal shows. If they disagree by more than rounding, dig into why before acting on either number.
Your original grant agreement is the legal source of truth. The portal is a display layer built on top. In a rare dispute, the agreement wins.
See how a 4-year cliff schedule works for the structural background, or the difference between vested vs exercised vs owned before you act on the number you've just calculated.
Doing the math on a Tuesday afternoon when you happen to remember is useful. But each actual vest event is a moment to make a decision, and those slide past without warning. Set a reminder for each one — or at least each anniversary — and the math becomes part of a workflow instead of a one-off curiosity.
See the full stock options vesting reminder workflow.
Set a reminder for your next vest date.
Done in seconds. No sign-up required.
You need four numbers: grant date, total shares granted, cliff length, and vesting frequency (monthly or quarterly). Before the cliff, vested = 0. On the cliff date, 25% vests. After that, add one tranche (1/48 for monthly, 1/16 for quarterly) for each elapsed period since the cliff.
Cumulative vested = 25% + (months since cliff × 1/48 × total shares). For example, 18 months after a 10,000-share grant's start date — that's 6 months past the 1-year cliff — you have 2,500 + (6 × 208) = 3,748 shares vested.
After the cliff, each quarterly tranche is 1/16 of the total grant (vs 1/48 for monthly). Quarterly events are larger but less frequent. Use the same approach: 25% at the cliff, then add 1/16 for each completed quarter since the cliff.
Your equity portal — Carta, Shareworks, Pulley, AngelList Stack — shows the schedule and your current vested count. Your original grant agreement is the legal source of truth. If they disagree, the grant agreement wins.
Usually no — vesting fires on specific anniversary dates, not continuously. Most schedules round to the vest event before the date you're checking. A few companies prorate for unusual cases (acquisitions, certain terminations), but the default is "what's vested as of the last completed event."
It's the cumulative percentage of your total grant that has vested as of a given date. 40% vested on a 10,000-share grant means 4,000 shares have vested. The remaining 6,000 are still unvested and tied to your continued employment.
Each grant has its own clock — its own grant date, cliff, and schedule. Refresher grants don't add to the original grant; they run in parallel. Calculate each separately, then sum the vested counts. This is why people with multiple grants often miss tranches: each one is on a different cadence.
Free. No account. Set a reminder for each vest event so the number in your portal stops being a surprise.
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