Does this handle all NIIT rules?

No. It’s a simplified base calculation. Detailed rules may adjust NII/AGI components.

Are thresholds current?

These are standard NIIT thresholds; update if rules change.

No. Use tax software or a professional for filing accuracy.

Not included. NIIT is federal; state taxes are separate.

How does this interact with gains/losses?

Enter net investment income after gains/losses; NIIT base uses that NII.

finance calculator

Net Investment Income Tax (NIIT) Calculator

Estimate NIIT (3.8%) based on net investment income, AGI, and filing status thresholds.

Results

NIIT threshold: $250,000
AGI above threshold: $0
NIIT base (lesser of NII or excess AGI): $0
Estimated NIIT (3.8%): $0

How to use this calculator

Enter net investment income.
Enter AGI and select filing status.
Review threshold, excess AGI, NIIT base, and NIIT amount.

Inputs explained

Net investment income: Interest, dividends, capital gains, rentals (non-RE pro), etc. simplified here.
AGI: Adjusted gross income; determines excess above threshold.

How it works

Thresholds (simplified): $200k single/HOH, $250k MFJ. Excess AGI = max(0, AGI − threshold). NIIT base = min(NII, excess AGI). NIIT = NIIT base × 3.8%.

Formula

Threshold = based on filing status
Excess AGI = max(0, AGI − Threshold)
NIIT base = min(NII, Excess AGI)
NIIT = NIIT base × 3.8%

When to use it

Checking NIIT exposure for high earners with investment income.
Planning capital gains/loss harvesting with NIIT in mind.
Estimating NIIT when income crosses thresholds.

Tips & cautions

Use combined net investment income; losses reduce NII.
If AGI is below the threshold, NIIT is $0.
Combine with capital gains tools to see total tax impact.
Simplified; does not model deductions, exclusions, or special categories.
Thresholds current as of recent rules; update if they change.
Not tax advice; use tax software or a pro for filings.

Worked examples

$20k NII, $250k AGI, MFJ

Threshold $250k → Excess AGI $0
NIIT base = $0
NIIT = $0

$30k NII, $300k AGI, MFJ

Excess AGI = $50k
NIIT base = min(30k, 50k) = 30k
NIIT = 30k × 3.8% = $1,140

Deep dive

Estimate NIIT (3.8%) by entering net investment income, AGI, and filing status to see threshold, excess AGI, NIIT base, and tax.

Use it to check if investment income triggers NIIT and how much applies.

FAQs

Does this handle all NIIT rules?: No. It’s a simplified base calculation. Detailed rules may adjust NII/AGI components.
Are thresholds current?: These are standard NIIT thresholds; update if rules change.
Is this tax advice?: No. Use tax software or a professional for filing accuracy.
State/local taxes?: Not included. NIIT is federal; state taxes are separate.
How does this interact with gains/losses?: Enter net investment income after gains/losses; NIIT base uses that NII.

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Simplified NIIT estimate. Does not model all adjustments or special categories. Confirm with tax software or a professional for filings.