Safe harbor: pay 100% of last year’s tax (110% if AGI > $150k) to avoid penalties.
Example: Expected annual tax (income + SE): $24,000 · Withholding already planned: $0 · Prior-year total tax (safe harbor): $20,000 · AGI over $150k last year?: No → Pay per quarter: $5,000.
Annual safe-harbor amount: $20,000
Due dates: Apr 15 · Jun 15 · Sep 15 · Jan 15
Frequently asked questions
How do I calculate quarterly estimated tax? Safe harbor: pay 100% of last year’s tax (110% if AGI > $150k) to avoid penalties. Enter your numbers above and the result updates instantly. For example: Expected annual tax (income + SE): $24,000 · Withholding already planned: $0 · Prior-year total tax (safe harbor): $20,000 · AGI over $150k last year?: No → Pay per quarter: $5,000.
Is this Quarterly Estimated Tax Calculator free? Yes — completely free with no sign-up or paywall. It runs entirely in your browser and keeps working offline; the numbers you enter never leave your device.
How accurate is it? It uses the standard published formula for quarterly estimated tax. Results are estimates for planning — not financial, tax, medical, engineering, or legal advice.