How Property Taxes Are Calculated

Actual Value, Assessment Rate, and Mill Levy

Assessment Rate

The Assessment Rates below reflect rates for the tax years 2025 and 2026. These rates will impact taxes paid in 2026 and 2027. For more information on the 2025 and 2026 assessment rates, please visit the Division of Property Taxation’s Assessment Rates web page.

2025 and 2026 Assessment Rates and Value Reductions

Type of Property	2025 Assessment Rate	2025 Value Adjustment	2026 Assessment Rate	2026 Value Adjustment
Residential—school districts	7.05%	$0	7.05%	$0
Residential—local government	6.25%	$0	6.8%	10% of the first $700k in actual value
Business Personal Property	27%	$0	26%	$0
Agricultural	27%	$0	25%	$0
Commercial	27%	$0	25%	$0
Industrial	27%	$0	26%	$0
Vacant Land	27%	$0	26%	$0
Renewable Energy	27%	$0	25%	$0
Oil & Gas Production	87.5%	$0	87.5%	$0

Property Tax Calculations

2025 Residential Property Tax Calculation

Beginning in tax year 2025 (payable in 2026), there are two assessment rates: one for school districts and one for all other local government districts (fire districts, cities, etc.). For more information on the 2025 property tax calculation, please visit the Understanding Property Taxes in Colorado web page.

School Districts Calculation

Actual
Value
X
Schools
Assessment
Rate
=
Schools
Assessed
Value

and then

Schools
Assessed
Value
X
Schools
Mill
Levy
=
Schools
Taxes
Due

Local Government Districts Calculation

Actual
Value
X
Local Gov’t
Assessment
Rate
=
Local Gov’t
Assessed
Value

and then

Local Gov’t
Assessed
Value
X
Local Gov’t
Mill
Levy
=
Local Gov’t
Taxes
Due

Property Tax Calculation Total

School
Taxes
Due
+
Local Gov’t
Taxes
Due
=
Total
Taxes
Due

The example below is for a residential property with an Actual Value of $800,000 for tax year 2025, paid in 2026, with a Residential Assessment Rate of 7.05% for school districts, and 6.25% for local government. The school district’s Mill Levy is 30, and for all other local government districts that serve this property, the total Mill Levy is 65. The taxes would be calculated as follows:

School Districts Example

$800,000
X
7.05%
(or 0.0705)
=
$56,400

and then

$56,400
X
30
(or 30 Mills
or 0.03)
=
$1,692

Other Government Districts Example

$800,000
X
6.25%
(or 0.0625)
=
$50,000

and then

$50,000
X
65
(or 65 Mills
or 0.065)
=
$3,250

Property Tax Calculation Total

$1,692
+
$3,250
=
$4,942

Example: 2025 Residential Property Tax Calculation for Actual Value $800,000*

Taxing Authority	Actual Value	Assessment Rate	Assessed Value	Mill Levy	Tax Amount
School Districts	$800,000	7.05%	$56,400	30	$1,692
Local Governments	$800,000	6.25%	$50,000	65	$3,250
Total Tax	—	—	—	—	$4,942

2026 Residential Property Tax Calculation

In tax year 2026 (payable in 2027), there are two assessment rates; one for school districts and one for all other local government districts (fire districts, cities, etc.). There is also a value reduction for the local government portion of the actual value for residential properties. For more information on the 2026 property tax calculation, please visit the Understanding Property Taxes in Colorado web page.

School Districts Calculation

Actual
Value
X
Schools
Assessment
Rate
=
Schools
Assessed
Value

and then

Schools
Assessed
Value
X
Schools
Mill
Levy
=
Schools
Taxes
Due

Local Government Districts Calculation

(
Actual
Value
–
Value
Reduction
(when applies)
)
=
Local Gov’t
Reduced
Value

and then

Local Gov’t
Reduced
Value
X
Local Gov’t
Assessment
Rate
=
Local Gov’t
Assessed
Value

and then

Local Gov’t
Assessed
Value
X
Local Gov’t
Mill
Levy
=
Local Gov’t
Taxes
Due

Property Tax Calculation Total

School
Taxes
Due
+
Local Gov’t
Taxes
Due
=
Total
Taxes
Due

The example below is for a residential property with an Actual Value of $800,000 for tax year 2026, paid in 2027, with an assumed Residential Assessment Rate of 7.05% for school districts, and 6.8% for local government. The school district’s Mill Levy is 30, and for all other local government districts that serve this property, the total Mill Levy is 65. The taxes would be calculated as follows:

School Districts Example

$800,000
X
7.05%
or (0.0705)
=
$56,400

and then

$56,400
X
30
(or 30 Mills
or 0.030)
=
$1,692

Local Government Districts Example

(
$800,000
–
$70,000
)
=
$730,000

and then

$730,000
X
6.8%
or (0.068)
=
$49,640

and then

$49,640
X
65
(or 65 Mills
or 0.065)
=
$3,227

Property Tax Example Total

$1,692
+
$3,227
=
$4,919

Example: 2026 Residential Property Tax Calculation for Actual Value $800,000*

Taxing Authority	Actual Value	Assessment Rate	Assessed Value	Mill Levy	Tax Amount
School Districts	$800,000	7.05%	$56,400	30	$1,692
Local Governments	$800,000 (reduced value $730,000)	6.8%	$49,640	65	$3,227
Total Tax	—	—	—	—	$4,919

* These are examples. Senior Exemptions are not taken into account. For an accurate calculation of your property taxes, please reach out to the Treasurer’s office (Email: treasurer@bouldercounty.gov or call 303-441-3520)

Additional details on the Mill Levy are below. Seniors and disabled veterans may qualify for certain property tax exemptions that could impact their final tax amount.

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 properties within a school district’s boundaries as $100,000,000.
The school board of that school district 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), for that district’s portion of the total Mill Levy.
The school district’s tax rate is $13.98 in revenue needed for each $1,000 of assessed value.