What counts as a short-term capital gain?

A short-term capital gain arises when you sell a capital asset held for one year or less. The gain is taxed at ordinary income rates.

Does this include state taxes or NIIT?

No. Results show U.S. federal income tax only using ordinary rate schedules. The Net Investment Income Tax (3.8%) and state/local taxes are not included.

Are long-term gains treated differently?

Yes. Long-term gains have preferential brackets (0%, 15%, 20%) and a different computation. This tool focuses on short-term gains only.

How accurate is this calculator?

It computes federal tax using the 2024 IRS ordinary income tax schedules for your filing status and measures the difference with and without the gain. Special credits, AMT, NIIT, and other adjustments are not modeled.

Can I enter a loss instead of a gain?

This tool expects a non‑negative gain. Net capital losses have special rules: they first offset gains and then may reduce ordinary income up to $3,000 per year ($1,500 if MFS).

Where do the tax brackets come from?

From IRS Rev. Proc. 2023-34, which provides the 2024 inflation‑adjusted ordinary income tax rate schedules.

Capital Gains Tax Calculator (Short-Term)

Q: Which income figure should I enter?

Enter your taxable income before the gain—generally Form 1040, line 15 (for 2024)—after deductions and exemptions, but excluding the short-term gain you want to test.

Quickly estimate the federal tax impact of a U.S. short-term capital gain. This professional-grade tool calculates the additional tax due, your effective tax rate on the gain, and your marginal bracket using the 2024 IRS ordinary income tax schedules. Ideal for investors, advisors, and financial planners.

Calculator

Filing status

Tax year

Taxable income BEFORE the gain (USD)

Short-term capital gain amount (USD)

Federal income tax only. The Net Investment Income Tax (3.8%), AMT, credits, and state/local taxes are not included.

Results

Additional federal tax due on the gain $0.00

Effective tax rate on the gain 0.00%

New taxable income $0.00

Total federal tax after the gain $0.00

Marginal bracket after the gain —

Enter values and press Calculate to see your results.

Data Source and Methodology

Authoritative sources:

IRS Topic No. 409 — Capital Gains and Losses (Current). IRS.gov — https://www.irs.gov/taxtopics/tc409
IRS Revenue Procedure 2023-34 — 2024 Inflation Adjustments (including ordinary income tax rate schedules). Issued Nov 2023 — rp-23-34.pdf

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

$$ \text{Tax}(x)=\sum_{i=1}^{n} r_i \cdot \max\!\big(0,\ \min(x, u_i)-\ell_i\big) $$

$$ \Delta \text{Tax} = \text{Tax}(x+G) - \text{Tax}(x) $$

$$ \text{Effective Rate on Gain} = \frac{\Delta \text{Tax}}{G} $$

Where x is taxable income before the gain, G is the short‑term gain, r_i are the ordinary rates, and [ℓ_i, u_i] are the IRS bracket bounds for the chosen filing status.

Glossary of Variables

Filing status

IRS status used to determine bracket thresholds: Single, Married Filing Jointly, Married Filing Separately, Head of Household.

Tax year

The calendar year for which the ordinary rate schedules apply (currently 2024).

Taxable income (before gain)

Your taxable income prior to adding the short‑term gain (Form 1040, line 15 for 2024). After deductions and exemptions.

Short-term capital gain

Gain on assets held one year or less, taxed at ordinary rates.

Additional federal tax

The difference between your federal tax with and without the gain.

Effective tax rate on the gain

Additional tax divided by the gain amount.

Marginal bracket

The ordinary income rate that applies to the last dollar of your income after adding the gain.

Total federal tax after the gain

Progressive tax computed on your taxable income plus the gain.

How It Works: A Step-by-Step Example

Scenario: Filing status = Single; Taxable income before gain = $85,000; Short‑term gain = $12,000 (Tax year 2024).

Compute tax before the gain, Tax(85,000), by summing each bracket slice using the 2024 Single schedule.
Compute tax after the gain, Tax(97,000) = Tax(85,000 + 12,000).
Extra tax due: ΔTax = Tax(97,000) − Tax(85,000).
Effective rate on the gain: ΔTax ÷ 12,000.
Marginal bracket is the rate corresponding to the bracket containing $97,000 (22% in 2024 Single until $100,525).

This method exactly matches the formulas above and the IRS rate schedules.

Frequently Asked Questions (FAQ)

Is a short-term capital gain always taxed at ordinary rates?

Yes. Short‑term gains (assets held ≤ 1 year) are taxed as ordinary income at your marginal bracket for the tax year.

Should I include the standard deduction?

Yes, indirectly. Enter your taxable income after deductions and exemptions but before the gain. This aligns with Form 1040 taxable income.

Does this calculator include credits, AMT, or NIIT?

No. It models the ordinary progressive tax schedules only. Credits, AMT, the 3.8% Net Investment Income Tax, and state/local taxes are excluded.

What if my gain moves me into a higher tax bracket?

Only the portion of income within a higher bracket is taxed at that higher rate. The tool accounts for this by using bracket slices.

How are capital losses treated?

Net capital losses first offset gains. Remaining net losses may reduce ordinary income up to $3,000 ($1,500 if MFS) per year. This tool focuses on gains only.

Can I use this for long-term gains?

No. Long‑term gains use preferential rates and thresholds (0%, 15%, 20%) and require a different computation.

Which official sources does this rely on?

IRS Topic 409 (treatment of capital gains/losses) and IRS Rev. Proc. 2023‑34 (2024 ordinary rate schedules).

Strumento sviluppato da Ugo Candido. Contenuti verificati da CalcDomain Editorial Team.
Ultima revisione per l'accuratezza in data: September 13, 2025.