A-101 Property tax estimator · Connecticut
Know Your Build.
The same addition costs $5,835 a year in Hartford and $918 in Washington.
Six hundred square feet, built to the same spec. The only difference is the mill rate, and unlike the construction bill, this one arrives every July for as long as you own the house. Price yours below.
167 of 169 towns priced · FY 2025–26 rates · free, no signup
State average28.97mills, FY 25–26
Spread58.10Washington to Hartford
Below average93 towns56% of the state
Above average74 towns44% of the state
Full scheduleSheet A-102 ↗Sort, filter, compare
01 Scope of work
02 Site & scope figures
169 CT towns
Market value, not assessed
Added or newly built
Total construction cost, all in
03 Addition · -
Annual increase-
Per month-
New annual bill-
Over 30 years-
No reassessment expected
Assessors separate work that adds value from work that maintains it. Cosmetic work, like paint, flooring, and fixture swaps, is maintenance. It usually needs no permit, and the permit is what notifies the assessor in the first place. Without one, there is normally nothing to trigger a review of your property.
Two things can still change this. If your town's five-year revaluation happens to fall after your work, the whole house gets looked at regardless. And if the job grows into moved plumbing, a new bathroom, or finished space that was not finished before, it stops being cosmetic and becomes a capital improvement. Pick a higher grade above to price that version.
Where the $/sf figures come from
These rates are compiled from published 2026 Connecticut design-build and cost-guide figures. Be aware the real spread is wide. CT sources put additions anywhere from $125 to $550 per square foot, and the same 600 sf can differ by six figures depending on site conditions, room type and finish level. A bathroom costs far more per foot than a bedroom. Treat the grade rates as a starting bracket, not a quote, and replace them with a real contractor number as soon as you have one.
Read this before you trust the number
This applies your town's mill rate to an estimated value added, not an appraisal. Your assessor decides the real figure after the Certificate of Occupancy, and it lands on the following October grand list, so the first higher bill is usually 12 to 18 months out. Special fire or taxing districts are not included.
The full set · seven sheets
A-101
Estimator
Price the tax impact of your project, town by town.
You are here
A-102
Mill Rates
All 167 towns, sortable, with the spread laid bare.
A-103
Cost Build-Up
What construction actually costs, line by line, by grade.
Pro
B-101
Budget
Soft costs, contingency, and when the tax bill actually lands.
B-102
Permits
The sequence every CT building department follows.
C-101
Glossary
Grand list, mill, assessed value, plainly defined.
C-102
About
Who made this, where the data comes from, and what it can't tell you.