Simple taxable brokerage model using long-term capital gains assumptions

US Taxable Brokerage Withdrawal Calculator

This page models a question generic FIRE calculators usually skip: how much do you actually need to sell from a taxable brokerage account to land on the cash you want after tax?

It is still simplified, but it is much closer to the real withdrawal problem than pretending gross portfolio math and spendable cash are the same thing.

Settings

Portfolio value when withdrawals begin ?

Cost basis at FIRE start ?

Desired monthly payout (after tax) ?

Expected annual return ?

Annual inflation ?

Federal long-term capital gains rate ?

State tax rate ?

Years to simulate ?

Tax starts in ?

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First taxable month ?

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Total estimated tax ?

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Average taxable-month tax ?

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Total withdrawal per month ?

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Ending account value ?

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Summary

Enter the brokerage value and cost basis you expect to have when FIRE withdrawals begin, then set the tax rates you want to test.

Portfolio over time

How The Simulator Works

The simulator starts from your taxable brokerage account at the point FIRE withdrawals begin. It applies monthly growth, then estimates the gross sale needed to deliver your chosen net monthly payout. Each sale is treated as a proportional mix of basis and unrealized gain based on the portfolio at that moment, which means only the gain portion is taxed. Federal long-term capital gains tax and your simplified state tax rate are then applied to that gain portion.

This is not financial advice. This is a planning tool, not a tax return calculator. Real US taxation can depend on filing status, other taxable income, qualified dividends, short-term gains, NIIT, tax-loss harvesting, state-specific rules, and lot-selection strategy. This v1 assumes long-term capital gains treatment for all taxable gains you realize from the account.

Important Notes

This v1 is built specifically for a US taxable brokerage account, not a Traditional IRA, 401(k), or Roth account.
The inputs should reflect the portfolio value and remaining cost basis when FIRE withdrawals begin, not necessarily what sits in the account today.
The model treats each sale as a proportional mix of basis and gain rather than specific tax lots.
Federal and state tax are simplified into the two rates you enter directly.
The calculator does not model ordinary income interactions, brackets, or penalties.
If your cost basis is close to the total account value, taxes may stay low for longer even while withdrawals continue.