What Is a Mill Levy in Colorado? A Plain-English Guide
Quick Answer
A mill levy is the tax rate applied to your property’s assessed value in Colorado. One mill equals $1 of tax per $1,000 of assessed value — so a mill levy of 85 mills on a $30,600 assessed value produces $2,601 in annual property tax. Your total mill levy combines rates from your county, school district, city, and all special districts covering your parcel.
What Is a Mill Levy, in Plain English?
When you get a Colorado property tax bill, it lists a mill levy — a number that looks like 78.450 or 102.68. That number is your tax rate, expressed in mills. One mill is one-tenth of a cent, or $0.001. Applied to property tax, one mill means you pay $1 for every $1,000 of assessed value.
Think of it this way: if your local government needs to collect a certain amount of revenue from property owners, it sets a mill levy high enough to collect that amount from the combined assessed value of all properties in its taxing district. The levy is not arbitrary — it is calculated based on budget needs divided by the total assessed value in the district.
Why the odd name? “Mill” comes from the Latin millesimum, meaning one-thousandth. It has been used in U.S. property tax systems since the 1800s. Colorado statute formalizes mill levies under C.R.S. §§ 39-1-111 through 39-1-119.
How a Mill Levy Is Calculated — With a Real Example
Colorado property tax uses a two-step calculation. First, your property’s actual (market) value is multiplied by the state assessment rate to get the assessed value. Then the mill levy is applied to that assessed value.
Colorado Property Tax Formula
Step 2 — School: Actual Value × 7.05% = Assessed Value
Step 3: Property Tax = (Assessed Value × Mill Levy) ÷ 1,000
Source: HB24B-1001 · Colorado DOLA · C.R.S. § 39-1-104
Real Example — $450,000 Home in Adams County
School district tax is calculated separately using 7.05% rate applied to full actual value. Total bill combines both. Estimate only — actual levy varies by specific parcel location.
⚠️ Mill levies change every year. Your county sets a new mill levy each November after local governments certify their budgets. The levy on your tax bill reflects the rate in effect when your bill was calculated — always check your current bill or county treasurer portal for the live figure.
Who Sets Mill Levies in Colorado?
No single authority controls your total mill levy. It is the sum of rates set by every government body that has taxing authority over your specific parcel. Two houses on the same street can have different total mill levies if one sits inside a different fire district or city boundary.
| Taxing Authority | Who Sets It | Typical Contribution | Example |
|---|---|---|---|
| School District | School board | 40–55 mills | Douglas County Re-1: 48 mills |
| County | County commissioners | 10–20 mills | Arapahoe County: 13.7 mills |
| City / Town | City council | 5–15 mills | Fort Collins: 9.8 mills |
| Fire District | Fire district board | 5–12 mills | South Metro Fire: 11.2 mills |
| Water District | Water district board | 1–6 mills | Denver Water: 3.4 mills |
| Library District | Library board | 1–4 mills | Jefferson County Library: 2.8 mills |
| Other Special Districts | District boards | Varies | Metro Districts, Sanitation, etc. |
Front Range metro areas — Denver, Aurora, Fort Collins, Colorado Springs — typically have 6 to 9 overlapping taxing authorities. Rural counties often have fewer, which partly explains why rural effective rates are sometimes lower despite similar assessment rates.
Colorado Mill Levies by County — Illustrative Comparison
The table below shows typical combined mill levies for major Colorado counties. These are illustrative figures — your actual mill levy depends on your city, school district, fire district, and any metro or special districts covering your parcel.
| County | Typical Combined Mill Levy | Illustrative Eff. Rate | Main Cities | County Page |
|---|---|---|---|---|
| Adams | ~106 mills | ~0.65% | Thornton, Westminster | Search → |
| Arapahoe | ~103 mills | ~0.64% | Aurora, Englewood | Search → |
| Boulder | ~104 mills | ~0.55% | Boulder, Longmont | Search → |
| Denver | ~107 mills | ~0.48% | Denver (city-county) | Search → |
| Douglas | ~82 mills | ~0.61% | Castle Rock, Parker | Search → |
| El Paso | ~90 mills | ~0.46% | Colorado Springs | Search → |
| Jefferson | ~98 mills | ~0.49% | Lakewood, Arvada, Golden | Search → |
| Larimer | ~95 mills | ~0.58% | Fort Collins, Loveland | Search → |
| Mesa | ~71 mills | ~0.45% | Grand Junction, Fruita | Search → |
| Pueblo | ~118 mills | ~0.68% | Pueblo | Search → |
| Weld | ~79 mills | ~0.56% | Greeley, Windsor | Search → |
Source: Colorado DOLA mill levy data, county treasurer records. Figures are illustrative — your parcel’s mill levy depends on its specific taxing district boundaries. Verify at DOLA →
How to Find Your Mill Levy in Colorado
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1Check your property tax bill Your annual tax statement from the county treasurer shows the mill levy applied to each assessed value. Look for a line labeled “total mill levy” or a breakdown by taxing authority.
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2Search your county assessor portal Search your property by address or parcel number. Most Colorado county assessors show the complete mill levy breakdown — school district, county, city, fire, and special district levies separately. Use our Property Search Guide for direct links to all 64 county portals.
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3Use Colorado DOLA’s mill levy database The Colorado Department of Local Affairs publishes annual mill levy data at dola.colorado.gov/lgis. Search by county and taxing district to see certified mill levies for any year.
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4Contact the county treasurer directly If you cannot locate your mill levy online, your county treasurer’s office can provide the exact levy for your parcel. This is the most authoritative source and is free to access.
Mill Levy vs Assessment Rate — What Is the Difference?
These two terms often get confused on property tax bills. They serve different functions in the Colorado property tax calculation.
Assessment Rate
State-Level · Set by Legislature
Converts your property’s actual (market) value into a taxable assessed value. In Colorado, the residential rate is 6.25% for local government and 7.05% for school districts. This rate is the same for every property in Colorado — it does not vary by county or city. Set by the Colorado General Assembly under C.R.S. § 39-1-104.
Mill Levy
Local-Level · Set by Each Authority
Applied to the assessed value to produce the final tax amount. Varies by parcel because each property sits within a unique combination of taxing districts. Two adjacent properties can have different mill levies if one is inside a city boundary or a different fire district. Set annually by each local taxing authority after budget certification.
💡 The key difference: The assessment rate is statewide and uniform. The mill levy is hyper-local and parcel-specific. When comparing property taxes across Colorado counties, the mill levy difference is almost always the reason — not the assessment rate, which is the same everywhere.