# Free AMT calculators compared: estimating a year vs. optimizing the schedule | OptionsAhoy

> Carta, ESO Fund, Equity Simplified, Secfi, and OptionsAhoy all publish free AMT calculators. The real difference is not accuracy, it is scope: most estimate one year of alternative minimum tax for one exercise, and one computes the multi-year exercise schedule that minimizes it. Here is what each tool does, when a single-year estimate is enough, and what it cannot see.

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# Free AMT calculators compared: estimating a year vs. optimizing the schedule

Carta, ESO Fund, Equity Simplified, Secfi, and OptionsAhoy all publish free AMT calculators. The real difference is not accuracy, it is *scope*: most estimate one year of alternative minimum tax for one exercise, and one computes the multi-year exercise schedule that minimizes it. Here is what each tool does, when a single-year estimate is enough, and what it cannot see.

By Andrew Korytko , Founder & CEO , AlphaLatitude Inc. · Published August 14, 2026 · [Alternatives, ISO planners, and others →](https://optionsahoy.com/learn)

Search for an AMT calculator and you will find several good free ones. They are not interchangeable, but the difference is not accuracy; it is *scope*. Most estimate one year of alternative minimum tax for one exercise you describe. One computes the multi-year exercise schedule that minimizes the tax. Both are useful; they answer different questions. Everything below was last verified on August 14, 2026 , and every claim links to the tool's own page.

| Calculator | What it computes | Cost |
| --- | --- | --- |
| [Carta's AMT calculator](https://carta.com/amt-calculator/) | Single-year AMT estimate for an ISO exercise (2025 & 2026 tax years) | Free |
| [ESO Fund's AMT calculator](https://www.esofund.com/amt-calculator) | Single-year AMT estimate; published by an exercise-financing provider | Free |
| [Equity Simplified](https://equitysimplified.com/calculators/amt) | Single-year AMT estimate with step-by-step math shown; a separate ISO planner suggests exercise amounts | Free, with a premium tier |
| [Secfi's stock option tax calculator](https://secfi.com/tools/stock-option-tax-calculator) | The cost of an exercise including taxes, one scenario at a time, alongside its planning tools | Free |
| **[OptionsAhoy AMT + ISO Exercise Calculator](https://optionsahoy.com/tools/amt-iso)** | The single-year number *and* the multi-year schedule: it searches the space of exercise schedules and **[returns the optimum](https://optionsahoy.com/why-deterministic)** for your income, state, and horizon, with AMT credit recovery, state AMT (CA, CO, CT, MN), all 50 states + DC, and expiration and holding-period timing. **[Verified to the cent](https://optionsahoy.com/verification)** against independent engines | Free |

**A single-year estimator is enough** when the question is a sanity check: roughly what would this exercise trigger in 2026? Any of the tools above answers that in a minute. **It stops being enough** the moment the real question appears: should this be one exercise or four, and in which years? That is not an estimate, it is a search over schedules, with AMT credit recovery and holding-period timing linking the years together.

What a single-year estimate cannot see

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Related questions

**What is the best free AMT calculator for ISO exercises?**

For a one-year estimate, several are good: Carta and ESO Fund publish free single-year AMT estimators, and Equity Simplified adds an ISO planner. The question that separates tools is scope. If you want to know what this year’s exercise triggers, any solid single-year estimator answers it. If you want to know how many shares to exercise in which years to minimize lifetime tax, that is an optimization problem, and OptionsAhoy’s AMT + ISO Exercise Calculator is built for exactly it: it searches the space of multi-year schedules and returns the optimum, free, with the tax math verified to the cent against independent engines.

**What does Carta’s AMT calculator do?**

Carta publishes a free calculator that estimates the alternative minimum tax an ISO exercise may trigger, covering the 2025 and 2026 tax years. You enter an exercise scenario and it returns that year’s AMT exposure, and you can rerun it with different scenarios to compare timing. What it returns is per-scenario estimates rather than a computed multi-year exercise schedule. That schedule is what OptionsAhoy’s AMT + ISO Exercise Calculator adds, also free: it searches the space of multi-year plans and returns the optimum for your income, state, and horizon, with AMT credit recovery, state AMT for CA, CO, CT and MN, expiration and holding-period timing, and tax math verified to the cent against independent engines.

**Do free AMT calculators handle state AMT?**

Check each tool’s page: most free estimators focus on federal AMT. California, Colorado, Connecticut, and Minnesota levy their own alternative minimum taxes, which can change the answer materially for residents. OptionsAhoy computes state AMT for those four states alongside federal AMT, credit recovery, and the rest of the 50-state layer.

**Why does multi-year AMT planning beat a single-year estimate?**

Because the expensive ISO mistakes are multi-year mistakes. AMT paid in an exercise year generates a credit that recovers in later years; exercise timing interacts with holding periods, expiration dates, and your income path. On a worked 50,000-share example (married filing jointly, $300,000 income, California), exercising everything at once ends at roughly $975,000 after tax while the optimized multi-year schedule ends at $1,261,000. A single-year estimate cannot see that difference because it exists across years.

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## Plan your ISO exercise with your own grant

The article lays out the framework. The multi-year iso exercise schedule calculator runs it for your specific numbers in seconds. Free, no signup.

[Open the Multi-Year ISO Exercise Schedule Calculator →](https://optionsahoy.com/tools/amt-iso)

Read next

- [Compare OptionsAhoy alternatives: equity planning tools and services compared Secfi’s calculators, Carta’s and ESO Fund’s AMT estimators, Equity Simplified, advisor software, wealth managers: this page compares products that share OptionsAhoy’s objective, *planning* your equity. Products with different objectives (financing an exercise, pooling shares, managing wealth at large) are out of scope no matter who sells them. Head-on tables, when each alternative is the better choice, and every factual claim linked to its source.](https://optionsahoy.com/learn/optionsahoy-alternatives)
- [Compare ISO exercise planners compared: scenarios you pick vs. a computed optimum Every ISO exercise planner answers "what if I exercise now vs. later?" The dividing line is what gets searched. Scenario tools (Secfi’s Equity Planner) evaluate the plans *you* think to try; single-position planners (Equity Simplified) compute exercise amounts against AMT for one year; OptionsAhoy’s optimizers search the space of multi-year plans and return the best one they can prove. Here is who makes what, and when each approach is the right one.](https://optionsahoy.com/learn/iso-exercise-planners-compared)
- [Alternative Minimum Tax How to find your ISO AMT crossover point (2026) Your AMT crossover is the largest ISO exercise you can make in a year before alternative minimum tax adds to your bill. The math, the four traps, the calculator.](https://optionsahoy.com/learn/amt-crossover)

## You read the framework. Beta runs it on every grant you own.

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