Coast FIRE
Whether the money already invested could compound its way to retirement.
Three decisions.
One clear number.
Test a retirement runway, estimate a tax refund, or compare renting with buying. Every assumption stays visible so the answer is useful—not mysterious.
Planning estimates, not adviceThese tools simplify taxes, markets and housing costs. Use official filings and a qualified professional before making a major decision.
Your coast number
The portfolio needed today to grow into your retirement target without another contribution.
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Using a real return keeps results in today's dollars.
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The projection contributes this amount until your portfolio reaches the coast threshold, then lets growth carry it.
Year-by-year compound growth
Portfolio value is separated into contributed capital and investment growth. Contributions stop at the first projected coast point.
U.S. tax refund estimator USD
A federal reconciliation using the total tax from your U.S. return estimate.
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Usually the total of Form W-2 box 2 and federal withholding on other forms.
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Use the “total tax” figure from current U.S. tax software, a preparer, or the applicable IRS form.
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Include quarterly estimated payments and an amount applied from last year's refund, without double-counting withholding.
Rent or buy?
Compare estimated ending net worth, including home equity and invested cash differences.
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Yearly mortgage amortization
Follow the remaining loan balance and see how each year's payments divide between principal and interest over the full amortization.
Learn the concepts behind the numbers
Short, example-driven explainers that pair with each calculator. Start with the guide, then go deeper.
U.S. tax refund
Why a refund happens, and how to tune withholding instead of lending to the IRS.
Rent vs. buy
Compare ending net worth with every cost on the table, not just the mortgage.