Capital Gains Tax Calculator 2026

The calculator measures gain as sale price minus purchase price, then applies different tax logic based on holding period. Short-term gains are estimated through ordinary-rate impact. Long-term gains are allocated across 0%, 15%, and 20% federal tiers based on your filing status and ordinary income.

It then estimates Net Investment Income Tax (NIIT) where income exceeds threshold levels, combines tax layers, and returns after-tax profit so you can compare strategies.

This structure makes it easier to test sell-timing scenarios before executing a taxable sale.

Why holding period is the biggest lever

For many investors, crossing from short-term to long-term treatment is the single most important tax lever. Short-term gains can be taxed at materially higher rates than long- term gains. A small timing change can create a noticeable difference in after-tax return.

That does not mean you should always delay selling. Portfolio risk, concentration, and cash-flow needs can justify immediate action. The goal is to understand tax cost clearly before deciding.

NIIT and high-income planning

High-income taxpayers may face NIIT on top of regular capital gains tax. NIIT is often overlooked in simple gain calculators, which can understate final liability. If your income is near threshold levels, modeling NIIT explicitly is important.

Coordinating salary timing, bonus expectations, and investment sale timing can sometimes reduce overlap in peak-income years.

Loss harvesting and offset strategy

Tax-loss harvesting can offset gains and improve after-tax outcomes, but rules such as wash-sale restrictions require careful execution. Good records and transaction-level tracking are essential.

A practical process is to estimate potential gains first, then evaluate whether realized losses or carryforwards can soften tax impact before year-end.

Planning beyond federal tax

State tax treatment varies widely. Some states tax gains as ordinary income, while others have no broad income tax. If you are considering relocation or large one-time sales, multi-state planning can materially change net proceeds.

Use this federal estimate as step one, then layer in state-specific tax analysis before final decision-making.