Calculateus

Section 179 Deduction Calculator

Calculate your allowable Section 179 deduction for immediately expensing qualifying business equipment.

Result

Section 179 Deduction
$200,000.00

Uses 2025 limits: a $1,250,000 maximum deduction, phasing out dollar-for-dollar once total qualifying purchases exceed $3,130,000 in a year. The deduction also can't exceed your business's taxable income for the year (though any excess can often carry forward) - this makes Section 179 primarily useful for profitable small and mid-sized businesses.

About the Section 179 Calculator

The Section 179 Deduction Calculator estimates how much of a qualifying equipment purchase a business can immediately expense in the year it's placed in service, rather than depreciating it over several years. It applies the 2025 dollar limit, the phase-out that kicks in for very large purchases, and the rule that ties the deduction to taxable business income.

How It Works

Enter the total cost of qualifying equipment purchased and the business's taxable income for the year before this deduction. The calculator starts from the $1,250,000 maximum Section 179 deduction, reduces it dollar-for-dollar for any equipment spending above the $3,130,000 phase-out threshold, caps the result at whatever the equipment actually cost, and then caps it again at the business's taxable income, since Section 179 can't be used to create a loss.

Phase-Out Reduction = max(Equipment Cost - $3,130,000, 0); Available Deduction = max($1,250,000 - Phase-Out Reduction, 0); Deduction Before Income Cap = min(Equipment Cost, Available Deduction); Final Deduction = min(Deduction Before Income Cap, max(Business Income, 0))

Formula & Methodology

The phase-out only starts reducing the $1,250,000 limit once total qualifying purchases exceed $3,130,000 for the year, and it reduces the limit dollar-for-dollar above that point, so a business spending $3,500,000 would see its limit fall by $370,000, to $880,000. That figure is then compared against the equipment's actual cost and the business's taxable income, with the smallest of the three values becoming the final deduction.

Examples

A mid-sized equipment purchase

A business buys $200,000 in qualifying equipment and has $250,000 in taxable income before the deduction. Since the purchase is well under the $3,130,000 phase-out threshold, the full $1,250,000 limit is available, but the deduction is capped at the $200,000 actually spent, all of which is fully usable against the $250,000 income.

A large purchase triggering the phase-out

A business buys $3,400,000 in equipment with $2,000,000 in taxable income. The phase-out reduces the available deduction by $270,000, the amount over $3,130,000, to $980,000. Taxable income exceeds that figure, so the final deduction lands at $980,000.

Advantages

  • Walks through all three limiting factors together, the flat cap, the phase-out, and the income limit, instead of requiring separate lookups to figure out which one actually binds.
  • Helps a business gauge whether a planned equipment purchase for the year is likely to hit the phase-out threshold before the purchase is finalized.
  • Shows how a lower-than-expected income year could unexpectedly cap a deduction that the equipment cost and phase-out math would otherwise fully allow.

Common Mistakes

  • Assuming the full $1,250,000 limit is always available, without checking whether total equipment purchases for the year exceed the $3,130,000 phase-out threshold.
  • Overlooking that the deduction can't exceed taxable business income, which can catch a business in a low-profit or loss year off guard.
  • Confusing Section 179 with bonus depreciation, two related but separately calculated provisions with different rules on income limitations.

Edge Cases to Watch For

  • Once equipment spending reaches $4,380,000 (the $1,250,000 limit fully offset by the phase-out), the available deduction hits zero, since the phase-out reduction equals or exceeds the maximum deduction itself.
  • If business taxable income is lower than the calculated deduction, the deduction is limited to that income figure, meaning Section 179 alone can't push a profitable year into a loss, even if the equipment cost and phase-out math would otherwise allow a larger write-off.
  • A negative or zero business income input results in a final deduction of zero, since the income cap floors at zero rather than allowing a negative deduction.
  • This calculator doesn't factor in bonus depreciation, which can apply to costs left over after Section 179 is exhausted and carries no income limitation of its own.

Common Use Cases

  • Small and mid-sized business owners planning equipment purchases before year-end for tax purposes.
  • Business accountants and bookkeepers estimating a client's available deduction across the flat cap, phase-out, and income limit.
  • Companies comparing whether a purchase amount would still qualify for the full deduction or start losing value to the phase-out.
Written & fact-checked by the Calculateus TeamLast updated August 5, 2026How we verify our formulas

Frequently asked questions

How is Section 179 different from bonus depreciation?

Section 179 lets you elect to expense specific assets up to the annual limit and is capped by business income, while bonus depreciation applies more broadly and automatically (unless you elect out) without an income limitation - many businesses use Section 179 first up to its limit, then apply bonus depreciation to remaining qualifying costs, since the two can be combined strategically.

Related calculators

Income Tax EstimatorEstimate your US federal income tax using 2025 marginal tax brackets.Self-Employment Tax CalculatorEstimate self-employment tax (Social Security + Medicare) on your net earnings.Sales Tax CalculatorCalculate sales tax and total price for a purchase.VAT CalculatorAdd or remove VAT from a price.

Related articles

Effective vs. Marginal Tax Rate: Why They're So DifferentThese two numbers are often confused, but they answer completely different questions. Here's how to calculate both correctly.What Your Marginal Tax Rate Actually MeansYour marginal tax rate is the rate on your next dollar of income, not your whole income. Here's why that distinction matters so much.How Property Tax Is Calculated on Your HomeProperty tax is based on assessed value, not market value — and the two aren't always the same number. Here's how it actually works.

Conclusion

The Section 179 Deduction Calculator lays out how the dollar cap, the large-purchase phase-out, and the taxable income limit interact to produce a single final number. It's a planning aid for equipment purchase timing, not a substitute for confirming eligibility rules with a tax professional.

References