Colorado Income Tax Calculator - Estimate Your CO State Tax

The Colorado income tax calculator estimates the state income tax on your Colorado return from your federal adjusted gross income. Colorado charges a single flat individual income tax rate of 4.40%, so the main work is finding your Colorado taxable income rather than climbing through brackets. That makes the estimate predictable: once you know your deductions, the state tax is 4.40% of the remainder.

• • Year-end planning: See what a raise or a new deduction does to your Colorado liability before you file Form 104.
• • Comparing filing options: Check how married filing jointly versus separately changes the standard deduction and the tax.
• • Validating withholding: Compare the annual state tax here against the Colorado withholding taken from your paychecks during the year.

Colorado builds its taxable income from your federal AGI, then subtracts Colorado additions and subtractions and the Colorado standard or itemized deduction. The federal AGI is the bridge between the two returns, which is why this calculator starts there. If you need to find that starting number first, the AGI calculator walks through how federal AGI is built.

Because Colorado has no progressive brackets for individuals and no local income tax, the state piece of your return is simpler than in many states. The flat 4.40% rate is set in statute and applies the same to every dollar of Colorado taxable income.

The calculator turns your federal AGI into Colorado taxable income, picks the larger of your standard or itemized deduction, subtracts any Colorado subtractions, and multiplies the result by 4.40%.

• Federal AGI: Your federal adjusted gross income, carried from your federal return as the starting point for Colorado taxable income.
• Deduction used: The Colorado standard deduction, which follows the federal amount, or your itemized deductions if they exceed the standard amount for your filing status and tax year.
• Other Colorado subtractions: Amounts Colorado lets you remove from AGI, such as the state income tax subtraction and a portion of military pay.
• Colorado tax: 4.40% of the positive Colorado taxable income after the deduction and subtractions.

Colorado's flat 4.40% rate is confirmed by the Colorado Department of Revenue, which administers the individual income tax and Form 104. The same rate applies whether your taxable income is $10,000 or $1,000,000.

The standard deduction follows the federal amount and is indexed for inflation each year, so the 2024, 2025, and 2026 figures differ. Married couples filing jointly receive twice the single amount, and married filing separately uses the single amount. If you want to see how the federal side is taxed before this state layer, the federal income tax calculator applies the federal brackets to the same AGI.

According to Colorado Department of Revenue, Colorado imposes a single flat 4.40% individual income tax rate and administers it through Form 104.

According to IRS Publication 17, Adjusted gross income (AGI) is the federally defined starting point that states such as Colorado build taxable income from.

A few terms decide almost everything about your Colorado result.

The per-paycheck version and the annual return are two views of the same 4.40% rate. The Colorado paycheck calculator shows the withholding taken from each check, while this tool shows the total annual liability on the return.

Colorado's state income tax subtraction lets many filers remove the Colorado tax itself from AGI, which matters for retirees and high earners whose state tax is large enough to matter.

You only need the numbers already on your federal return and a sense of your deductions.

1. 1 Pick the tax year: Choose 2024, 2025, or 2026 so the correct indexed standard deduction is applied.
2. 2 Choose your filing status: Select the status that matches your Colorado return; it sets the standard deduction amount.
3. 3 Enter federal AGI: Type your federal adjusted gross income from your federal Form 1040.
4. 4 Add subtractions and itemized deductions: Enter any Colorado subtractions and your itemized deductions if they exceed the standard amount.

A 2026 single filer with $60,000 AGI and no subtractions owes $1,947 after the $15,750 standard deduction.

The federal child tax credit and other credits reduce your federal bill, not your Colorado tax, but they are worth tracking alongside this estimate using the child tax credit calculator.

An annual estimate helps with planning well before April.

• • Clear state liability: You see the exact Colorado tax from your AGI without reading brackets or tables.
• • Filing-status comparison: Switching between married filing jointly and separately shows the deduction and tax difference immediately.
• • Deduction trade-offs: You can see how itemizing or a subtraction such as the state income tax subtraction changes the final tax.

Filing status can move the standard deduction a long way, especially for married couples. The marriage penalty calculator shows how federal brackets interact with joint versus separate filing, which is useful context before you decide how to file in Colorado.

Because the rate is flat, the calculator is also a quick what-if tool: raise AGI by $1,000 and state tax rises by $44, after the deduction. That linearity makes planning raises and retirement withdrawals straightforward.

The Colorado income tax calculator is most useful when you revisit it after a life change such as marriage, a new job, or starting Social Security, since each one shifts the deduction or a subtraction.

Three inputs move the answer the most.

• • This tool estimates the base Colorado tax and excludes any credits, Colorado additions, and the separate sales (transaction privilege) tax. Final liability is on Form 104.
• • The flat 4.40% rate is current law; a future rate change would require updating the rate used here.

Colorado's flat 4.40% rate means there is no bracket creep to worry about as income rises, which is the main difference from a state with graduated rates.

If you want to compare Colorado with another flat-rate state, the Illinois tax calculator applies that state's flat rate to a similar AGI-based base, which makes the structures easy to line up side by side. The Colorado income tax calculator is a planning estimate, so treat a real return as the final word where credits or additions apply.

According to Colorado Department of Revenue - Individual Income Tax, Colorado statute sets the flat individual income tax rate of 4.40% applied to Colorado taxable income.