Property Tax Calculation

How Property Taxes Are Calculated

Actual Value, Assessment Rate, and Mill Levy

Assessment Rate

The Current Assessment Rate below reflects rates for the 2022 tax year that will impact tax bills paid in 2023.

Type of Property Prior Assessment Rate Current Assessment Rate


Multi-Family housing
-Duplex/Triplex, 4 – 8 Unit Apartments, 9+ Units Apartments
7.15% 6.80%
All other residential property
-Single family, Condominiums, Townhomes
7.15% 6.95%


Hotel, motels and B&Bs 29% 29%
Renewable Energy Production 29% 26.4%
Agricultural Property 29% 26.4%
Vacant Land, Commercial and Industrial 29% 29%
Oil & Gas 87.5% 87.5%

Property Tax Calculation

Property taxes are calculated using the actual property value, the assessment rate, and the mill levy using the formula: Actual Value x Assessment Rate = Assessed Value x Mill Levy = Taxes Due. More information is available in the Calculating Your Property Taxes flyer. For example:
property tax calculation

For a residential property with an Actual Value of $350,000, an Assessment Rate of 6.8%,
and a Mill Levy of 86, there will be $2,049 in taxes due.

property tax calculation

Additional details on the Assessment Rate and Mill Levy are below. Seniors and disabled veterans may qualify for certain property tax exemptions.

Much more information on property taxes, including Property Tax Search, due dates, and paying taxes online, is available on the Boulder County Treasurer page.

Tax Rate or Mill Levy

The Tax Rate and Mill Levy are two different ways of expressing the same information. The Tax Rate is expressed as a percentage, while the Mill Levy is expressed in mills (1 mill = $1 of property tax for every $1,000 of assessed value)

Generally, properties are affected by several taxing entities. Each taxing entity determines what revenues will be required to operate during the coming fiscal year. The required revenues are then divided by the total assessed value to determine the tax rate/mill levy for each entity. To determine the total tax rate for a property, add the tax rates for each entity that impacts a property.

Mill Levy Example:

    • The assessor determines the total assessed value for the county as $100,000,000.
    • The Board of County Commissioners determines the budgeted property tax revenues needed are $1,398,000.
  • $1,398,000 (tax revenue) divided by $100,000,000 (assessed value) = 1.3980% Tax Rate, or 13.98 Mills (Mill Levy)
  • The county tax rate is $13.98 in revenue needed for each $1,000 of assessed value

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