Capital Gains Tax for Families: 2026 Calculator & Planning Guide

Long-term capital gains are taxed more favorably than ordinary income — but the rate you pay depends on your total household income, and the 3.8% NIIT threshold has never been adjusted for inflation. This guide explains the 2026 LTCG rules, calculates your actual tax exposure, and identifies planning windows most dual-income families miss.

2026 long-term capital gains tax calculator

Enter your household's ordinary income, the amount of long-term capital gains you expect, and your state's capital gains rate. The calculator applies the 2026 federal LTCG brackets and checks NIIT exposure based on your MAGI.

2026 federal LTCG rate brackets (married filing jointly)

Long-term capital gains — assets held longer than one year — are taxed at preferential rates that are lower than ordinary income rates. The rate depends on your total taxable income, including the gains themselves.¹

The NIIT: 3.8% surcharge that hasn't moved in 13 years

The Net Investment Income Tax (IRC §1411) adds 3.8% on investment income — dividends, interest, capital gains, rents — when your modified adjusted gross income exceeds $250,000 for married filers. Unlike almost every other tax threshold, this one was set in 2013 and has never been indexed for inflation. More families cross it every year.²

For a family selling appreciated stock or RSUs at $260,000 of MAGI, the federal rate on those gains isn't just 15% — it's 15% + 3.8% = 18.8%. For a family at $620,000, it's 20% + 3.8% = 23.8%. State taxes are added on top of that.

NIIT planning moves

• Pre-tax 401(k) contributions reduce MAGI. If your MAGI is $260K and you have $20K in investment income, increasing pre-tax 401(k) contributions by $10K drops MAGI to $250K and eliminates NIIT on those gains — a savings of $380 per $10,000 of contributions shifted.
• Timing of gain realization. If you're close to $250K, push large asset sales into a calendar year where income is lower — parental leave, a job change, or early in a year before a year-end bonus vests.
• Municipal bond interest is excluded from NIIT. For families above the threshold, munis avoid both ordinary income tax and the NIIT, making the after-tax yield comparison more favorable at higher income levels.
• Roth conversions in lower-income years reduce future NIIT exposure. Large pre-tax 401(k) balances generate mandatory distributions (RMDs) at 73+ that inflate MAGI in retirement, potentially pushing you over $250K. Converting pre-tax dollars to Roth now reduces future RMD-driven NIIT. See the Roth conversion strategy guide.

Home sale: the $500,000 capital gains exclusion

The §121 exclusion lets married couples exclude up to $500,000 of capital gain from the sale of a primary residence from federal tax — no capital gains tax, no NIIT, provided you meet the ownership and use tests (owned and lived in the home for at least 2 of the last 5 years).³

For families who bought a home 5–10 years ago and have seen significant appreciation, this exclusion is often the largest single tax benefit available. A few planning considerations:

• The exclusion applies per sale, not per person. A married couple gets $500K of exclusion on each qualifying primary residence sale. If you downsize, the exclusion applies to that sale. If you upsize and later sell, the exclusion applies again on the next primary residence (once the 2-of-5-year test is re-met).
• Depreciation recapture for home offices is not excluded. If you've claimed a home office deduction, the depreciation taken is recaptured as ordinary income (§1250), not excluded under §121. This is typically a small amount but worth flagging.
• Gain above $500K is taxed at LTCG rates. In high-appreciation markets, gains can exceed $500K. That excess is taxed at 15% or 20% + NIIT. Some families in this situation consider installment sales or opportunity zone investments to defer or reduce the taxable gain.
• Partial exclusion for short ownership. If you must sell before 2 years (job change, health, divorce, unforeseen circumstances), you can qualify for a partial exclusion equal to $500K × (months owned ÷ 24). A family forced to sell after 18 months would exclude 75% of $500K = $375,000.

The 0% bracket: a planning window most families underuse

Families whose taxable income (ordinary income after deductions) stays below $98,900 can realize long-term capital gains at 0% federal tax. For most dual-income households earning $200K+, the ordinary income alone pushes them well past this threshold — but there are specific windows where the 0% bracket opens up.

When the 0% bracket applies to families

• Parental leave: One spouse takes unpaid or partially-paid leave. Total household income drops. If taxable income from wages + other income is below $98,900, any gains realized in that calendar year are tax-free federally. See the parental leave planning guide for how to coordinate.
• Job transition: A gap between jobs — especially if the lower-earning year spans January through late fall — can create several months where ordinary income is depressed. Realize gains in that year rather than the following year when full income resumes.
• One spouse stays home: A single-earner household at $130,000 in wages has roughly $97,800 in taxable income after the $32,200 standard deduction — just under the $98,900 threshold. This household can realize up to $1,100 in capital gains tax-free. At $110,000 in wages, the room opens to ~$21,100.
• Early retirement phase: Families who retire before Social Security starts (age 62–70) have a low-income window where Roth conversions and 0%-bracket gain harvesting work in tandem. See the Roth conversion strategy for the full framework.

Capital gains situations unique to families

RSU and ESPP vestings

Restricted stock units vest and are taxed as ordinary income at vesting. But if you don't sell immediately — and the stock appreciates — any subsequent gain is a long-term capital gain if held more than a year. For families in the $200K–$400K range, that gain is typically taxed at 15% federally plus NIIT if MAGI exceeds $250K. The key question: does it make sense to hold RSUs for the preferential LTCG rate, or does the concentration risk outweigh the tax savings? See the RSU tax planning guide for the full analysis.

ESPP shares with qualified disposition

If you hold ESPP shares for at least 2 years from the offering date and 1 year from the purchase date, the discount portion is taxed as ordinary income but limited to actual gain — and appreciation beyond the purchase price is long-term capital gain. For a $100 stock purchased at $85 and later sold at $125, the $15 discount is ordinary income and the $40 gain is LTCG. The ESPP tax guide covers the qualifying vs. disqualifying disposition comparison in detail.

ISO exercises and AMT

Incentive stock options (ISOs) have a unique interaction with capital gains: a qualifying disposition (held 2+ years from grant, 1+ year from exercise) converts the entire gain to long-term capital gain. However, the spread at exercise creates an AMT preference item — potentially triggering AMT in the exercise year. The ISO planning guide explains the safe exercise limit calculator for families.

Selling the family home with gain above $500K

In markets like the Bay Area, Seattle, Austin, or Boston, a family can clear the $500K exclusion limit — particularly if they bought 10+ years ago. The gain above $500K is taxed at 15% (or 20% + NIIT at high income). Options to manage this: qualified opportunity zone investments (deferral until 2026 for pre-2027 investments), installment sales for income-producing property, charitable remainder trusts for larger gains, or simply modeling whether the tax still makes the sale worthwhile.

Short-term vs. long-term: the holding period matters

Short-term capital gains (assets held 1 year or less) are taxed as ordinary income — the same as your wages. At typical family income levels of $200K–$400K, the marginal rate on ordinary income is 24%–32%. Holding an asset past the 1-year mark converts that ordinary income rate to 15% (for most families in this income range) — a difference of 9–17 percentage points.

For RSUs: selling immediately at vesting means you're selling at the same price as the ordinary income recognition — no capital gain or loss. Holding for more than a year from the vesting date, any additional appreciation is taxed at LTCG rates. Holding for less than a year, any gain is short-term.

Tax-loss harvesting basics

Capital losses offset capital gains dollar-for-dollar. If you realize $10,000 of gains in a year but also harvest $10,000 of losses, you owe no capital gains tax on those gains. If losses exceed gains, up to $3,000 of net capital losses can offset ordinary income per year; excess losses carry forward indefinitely.

The wash-sale rule (IRC §1091) prevents the loss deduction if you repurchase the "substantially identical" security within 30 days before or after the sale. The solution: swap into a highly correlated but not identical position — for example, selling the Vanguard S&P 500 ETF (VOO) and buying the iShares Core S&P 500 (IVV) — then swapping back after 31 days if desired. See the taxable investing guide for more detail on wash-sale mechanics.

How a fee-only advisor helps with capital gains planning

Capital gains planning requires modeling multiple variables simultaneously: your ordinary income, expected gains, NIIT threshold proximity, state tax rates, other deductions, Roth conversion opportunities, and multi-year income projections. Doing this manually with a spreadsheet is possible — but an advisor who does this annually for clients will identify the optimal sequencing of realizations, conversions, and deferrals in a way most families miss on their own.

Specifically, a fee-only advisor — who charges by the hour or as a flat retainer, rather than a percentage of assets managed — will:

• Model which calendar year minimizes total tax on planned asset sales (RSUs, home, concentrated positions)
• Identify the Roth conversion amount that fills the gap without triggering NIIT or pushing the family into the 20% LTCG bracket
• Coordinate tax-loss harvesting across the whole portfolio, not just individual positions
• Flag depreciation recapture, AMT exposure from ISO exercises, and other interaction effects