State Income Tax Estimator (Detailed) Formula

Understand the math behind the state income tax estimator (detailed). Each variable explained with a worked example.

Use the State Income Tax Estimator (Detailed)

Formulas Used

Estimated State Tax

state_tax = state_taxable * state_rate / 100

Estimated Federal Tax

federal_tax = gross_income * federal_rate / 100

Combined Tax Burden

combined_tax = state_taxable * state_rate / 100 + gross_income * federal_rate / 100

Combined Effective Rate

combined_rate = gross_income > 0 ? (state_taxable * state_rate / 100 + gross_income * federal_rate / 100) / gross_income * 100 : 0

After-Tax Income

take_home = gross_income - state_taxable * state_rate / 100 - gross_income * federal_rate / 100

Variables

VariableDescriptionDefault
gross_incomeGross Annual Income(USD)80000
state_rateState Tax Rate(%)5
state_deductionState Standard Deduction(USD)5000
federal_rateApprox Federal Effective Rate(%)15
state_taxableDerived value= max(gross_income - state_deduction, 0)calculated

How It Works

State Income Tax Overview

State income tax rates vary dramatically across the US.

No Income Tax States

Alaska, Florida, Nevada, South Dakota, Texas, Washington, Wyoming (New Hampshire and Tennessee tax only investment income)

Flat Tax States

Colorado (4.4%), Illinois (4.95%), Indiana (3.05%), Michigan (4.25%), North Carolina (4.5%), Pennsylvania (3.07%), Utah (4.65%)

Highest Tax States

California (up to 13.3%), Hawaii (up to 11%), New Jersey (up to 10.75%), New York (up to 10.9%)

Combined Burden

Total Tax = Federal Tax + State Tax

State taxes may be deductible on federal return (SALT deduction, capped at $10,000).

Worked Example

$80,000 income, 5% state rate, $5,000 state deduction, 15% federal effective rate.

gross_income = 80000state_rate = 5state_deduction = 5000federal_rate = 15
  1. 01State taxable = $80,000 - $5,000 = $75,000
  2. 02State tax = $75,000 x 5% = $3,750
  3. 03Federal tax = $80,000 x 15% = $12,000
  4. 04Combined = $3,750 + $12,000 = $15,750
  5. 05Combined rate = $15,750 / $80,000 = 19.7%
  6. 06Take-home = $80,000 - $15,750 = $64,250

Ready to run the numbers?

Open State Income Tax Estimator (Detailed)