Business · Startup equity
Vesting schedule calculator.
How many shares have vested after a cliff and monthly vesting, and what would acceleration add? Everything runs in your browser.
A 48,000-share grant that vests over 48 months with a 12-month cliff has 0 vested before month 12, 12,000 at the cliff, then 1,000 a month. Leaving at month 30 means 30,000 vested; if 100% of the unvested shares accelerate at a sale in month 30, all 48,000 vest.
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How the schedule works
Vesting means earning the right to equity over time. Wikipedia describes the most common startup-style schedule as pro-rata monthly vesting over the period with a six or twelve month cliff: nothing vests before the cliff date, then the portion earned so far vests at once. This calculator uses that structure. Vested shares at month m (at or after the cliff) are floor(grant x m / total months), and zero before the cliff. The 48-month, 12-month-cliff default is a common rule of thumb, not a published standard; enter whatever your agreement says.
Acceleration is when some of the still-unvested shares vest early, for example at a sale of the company. The toggle applies your chosen percent to the shares unvested at the event month. Whether your grant has acceleration, and what triggers it, is set by your documents.
Worked example
Grant 48,000, total 48 months, cliff 12. Before month 12: 0 vested. At month 12: 48,000 x 12 / 48 = 12,000. From then, 1,000 a month. At month 30: 30,000 vested and 18,000 unvested. With acceleration at 100% of the unvested shares, the remaining 18,000 vest and the total is 48,000; at 50% it is 9,000 more, 39,000 in all. Leaving at month 11 means nothing vests because the cliff has not been reached.
Limits
This calculator handles one grant with monthly vesting. It does not model quarterly or annual schedules, back-dated vesting start dates, different cliffs for part of a grant, leaves of absence, or post-termination exercise windows. For options, vesting is separate from the cost of exercising them, which the exercise cost calculator covers. Tax at vesting or exercise depends on your jurisdiction and the type of award and is left to a professional; the Cooley GO glossary explains why timing matters for US Section 83(b) elections.
Sources, opened 8 October 2026: Wikipedia, Vesting (cliff vesting as a period before benefits vest; "the vesting schedule is most often a pro-rata monthly vesting over the period with a six or twelve month cliff"); Cooley GO glossary, 83(b) Election (equity earned through vesting is treated as taxable income by the IRS if worth more than paid for it).
Frequently asked questions
How does a 4-year vesting schedule with a 1-year cliff work?
Nothing vests for the first 12 months. At month 12, 12/48 (25%) of the grant vests at once. After that, 1/48 of the grant vests each month until month 48. The four-year length is a common convention, not a standard.
What is a vesting cliff?
A cliff is a period at the start during which nothing vests. If you leave before it ends, you keep none of the grant. Wikipedia notes monthly vesting with a six or twelve month cliff is the most common pattern.
What does acceleration do?
Acceleration vests some of the unvested shares early when a defined event happens, such as a sale of the company. Your agreement sets whether it applies and how much.
How many shares vest if I leave at month 30?
On a 48,000-share, 48-month grant with a 12-month cliff, 30,000 shares have vested at month 30 and 18,000 are unvested.
Is vesting the same as owning?
Vested options still have to be exercised, which costs the strike price, and shares can have other restrictions. Taxes depend on your jurisdiction. Ask your advisers.
Educational only. Not legal, tax or investment advice.
Planning and learning aid only. Real terms depend on the signed documents and your jurisdiction. Tax treatment (409A valuations, 83(b) elections, ISOs and similar) is left to a qualified professional. Amounts are in any one currency; the symbol is only a label.