Colorado State Income Tax Calculator
Use our Colorado income tax calculator to estimate your 2024–2025 state tax. Mobile-first, WCAG-compliant tool with clear methodology, formulas, and FAQs.
Change any field and re-run the calculation to see how deductions, credits, and tax years alter your Colorado state tax.
How to Use This Calculator
Enter your filing status, tax year, income, deductions, and credits. The form mirrors how Colorado starts with federal taxable income (after the federal standard deduction or your itemized total) and then applies the flat 4.40% rate. Results refresh immediately when you click Calculate or change an input.
Methodology
The calculator follows the Colorado Department of Revenue guidance: compute adjusted gross income, subtract the higher of standard or itemized deductions, then multiply the taxable income by Colorado‘s flat 4.40% rate for 2024–2025. Credits reduce tax without dropping below zero; pre-tax deductions are limited to non-negative values, and all currency fields round to two decimal places.
- AGI is capped at a minimum of zero after subtracting pre-tax deductions.
- Deductions use the federal standards by year (see glossary) unless you provide an itemized amount.
- Credits are never refundable in this model and are capped so the final tax owed cannot go negative.
Results are estimates for planning purposes only. Consult the Colorado Department of Revenue or a tax professional for certified guidance.
Data Source and Methodology
Authoritative source: Colorado Department of Revenue, Individual Income Tax Guide (DR 0104). Calculations mirror the flat rate methodology described in the publication.
- Colorado applies a flat state income tax rate to Colorado taxable income.
- Colorado taxable income starts from federal taxable income, which already includes the standard deduction or itemized deductions.
- This calculator models that approach with a toggle between Standard and Itemized deductions and the 4.40% rate for the selected year.
Glossary of Variables
- Annual gross income: Total income before pre-tax deductions.
- Pre-tax deductions: Contributions that reduce federal taxable income (401(k), HSA, etc.).
- Standard deduction: Federal standard deduction amount based on year and filing status.
- Itemized deductions: Your actual itemized total if you choose that route.
- Colorado taxable income (TI): AGI minus the selected deduction, floored at zero.
- Credits: Colorado credits applied after tax calculation (capped to the pre-credit tax).
- Effective state tax rate: Tax owed divided by gross income when gross income is positive.
How It Works: A Step-by-Step Example
Scenario: Tax Year 2024, Single, $85,000 gross income, $6,000 pre-tax deductions, standard deduction, $200 credits.
- AGI = max(0, $85,000 − $6,000) = $79,000
- Standard deduction (2024 Single) = $14,600
- Taxable income TI = max(0, $79,000 − $14,600) = $64,400
- Tax before credits = $64,400 × 4.40% = $2,833.60
- Credits applied = $200 → Tax owed = $2,633.60
- Effective rate = $2,633.60 / $85,000 ≈ 3.10%
Frequently Asked Questions (FAQ)
Is the Colorado state income tax flat?
Yes. Colorado levies a flat rate of 4.40% for 2024 and 2025 on Colorado taxable income.
How does the calculator treat the standard deduction?
It mirrors the federal treatment: select Standard or Itemized. The standard deduction value is pulled from the IRS tables for the chosen filing status and year.
Can I model itemizing?
Yes. Switch to Itemized and enter your annual total to compare with the standard deduction.
Are other taxes included?
No. This tool focuses solely on Colorado state income tax. Local taxes, TABOR refunds, and federal liabilities are excluded from these results.
What if my credits exceed the pre-credit tax?
The tool caps credits so the tax owed never goes below zero. Some credits may be refundable in reality; refer to the Colorado Department of Revenue for those cases.
Where can I verify the 4.40% rate and deductions?
See the Colorado Department of Revenue’s Individual Income Tax Guide (tax.colorado.gov/individual-income-tax-guide).