US Capital Gains Tax & 401k Growth Calculator — Free, Private, No Signup

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Two new US finance calculators just dropped — both run entirely in your browser with zero data collection. Perfect for tax season and retirement planning.

Capital Gains Tax Calculator

Calculate federal capital gains tax on stocks, crypto, and real estate investments.

Features:

Short-term vs long-term capital gains rates (2026 brackets)
All filing statuses: Single, MFJ, MFS, Head of Household
Net Investment Income Tax (NIIT) 3.8% surtax calculation
Multiple asset support — add all your investments at once
Visual pie chart showing profit vs tax breakdown
Handles capital losses with $3,000/year deduction note

Tax rates covered:

Short-term: 10%, 12%, 22%, 24%, 32%, 35%, 37% (ordinary income)
Long-term: 0%, 15%, or 20% based on income bracket
NIIT: Additional 3.8% for high earners ($200K+ single / $250K+ MFJ)

401k Growth Calculator

Project your 401k balance at retirement with employer match, compound growth, and salary increases.

Features:

11 inputs covering every variable that affects 401k growth
Year-by-year projection with IRS contribution limits
Catch-up contributions automatically applied at age 50+
Interactive line chart showing balance growth over time
Pie chart breaking down: your contributions vs employer match vs investment growth
"What if +1%?" scenario — see how much extra 1% contribution adds over your career
Full year-by-year breakdown table

Example: A 30-year-old earning $75K contributing 6% with a 50% employer match at 7% return = approximately $1.2M by age 65. Increase to 7%? That one percent adds ~$100K+ to your retirement.