What This Calculator Does
You bought a house for $350,000. The county sends you a tax bill for $5,250 every year. Where does that number come from? Property tax is not a flat percentage of what you paid. It is the product of an assessed value, a local tax rate measured in mills, and any exemptions you qualify for. This calculator breaks that math open so you can see exactly how your bill is built.
Enter your home market value, the assessment ratio your jurisdiction uses, the millage rate, and any homestead or senior exemptions. The tool returns your assessed value, taxable value, annual tax, monthly tax, and the effective tax rate as a percentage of market value. That last number is the one to watch, because it lets you compare your burden against other counties or states on an apples-to-apples basis.
According to the Tax Foundation, the average American household pays about $1,800 per year in property taxes, but the spread between the lowest and highest states is enormous. New Jersey homeowners pay an effective rate near 2.23%, while Hawaii owners pay around 0.32%. The same house can cost ten times more in tax depending on the address.
Inputs Required
- Home Market Value: The current fair market value of your property
- Assessment Ratio: The percentage of market value your assessor uses as the assessed value. Many states use 100%, but some use a fraction.
- Millage Rate: The local tax rate in mills. One mill equals $1 of tax per $1,000 of assessed value.
- Exemptions: Dollar reductions to assessed value from homestead, senior, disability, or veteran exemptions
Outputs Provided
- Assessed Value: Market value multiplied by the assessment ratio
- Taxable Value: Assessed value minus exemptions
- Annual Property Tax: Taxable value multiplied by the millage rate divided by 1,000
- Monthly Property Tax: The annual bill divided by 12, useful for escrow planning
- Effective Tax Rate: Annual tax as a percentage of market value
How the Calculation Works
Property tax follows a three-step formula. First the assessor determines your assessed value. Then exemptions are subtracted to get the taxable value. Finally the millage rate is applied.
Assessed Value = Market Value x Assessment Ratio
Taxable Value = Assessed Value - Exemptions
Annual Tax = Taxable Value x (Millage Rate / 1000)
The millage rate is the part that confuses people. A mill is one-tenth of a cent. A rate of 15 mills means $15 of tax per $1,000 of taxable value, which is the same as 1.5%. If your taxable value is $350,000 and your rate is 15 mills, your annual tax is 350,000 x 15 / 1000 = $5,250.
The assessment ratio matters because some states do not tax the full market value. Michigan assesses at 50% of market value, so a $200,000 home has an assessed value of $100,000. California caps assessed value increases under Proposition 13, so a long-time owner may have an assessed value far below current market value. Always check your local assessor's website for the ratio that applies to you.
How to Use the Calculator
- Enter your home's current market value. Use a recent appraisal, sale price, or Zillow estimate as a starting point.
- Set the assessment ratio. If you are unsure, leave it at 100% and adjust the millage rate to match your actual bill.
- Enter your millage rate. You can find this on your tax bill or your county assessor's website. It is often broken into county, school, and municipal portions that you add together.
- Add any exemptions you receive. Homestead exemptions are common and can range from a few thousand dollars to tens of thousands.
- Read the annual and monthly tax figures. The effective rate tells you how your burden compares to other areas.
Example Calculations
Example 1: A New Jersey Suburban Home
Maria owns a $450,000 colonial in Essex County, New Jersey. Her assessment ratio is 100%, and her total millage rate is 24.5 mills. She has no exemptions. Her assessed value is $450,000, her taxable value is $450,000, and her annual property tax is 450,000 x 24.5 / 1000 = $11,025. That is $919 per month, which is more than many people's car payment. Her effective rate is 2.45%, well above the national average.
Example 2: A Texas Home With Homestead Exemption
James bought a $300,000 home in Dallas, Texas. Texas assesses at 100% of market value. His millage rate is 18 mills, and he qualifies for the general homestead exemption of $25,000 plus a 10% school-district homestead exemption. For simplicity, entering the $25,000 flat exemption: assessed value is $300,000, taxable value is $275,000, and annual tax is 275,000 x 18 / 1000 = $4,950. Without the exemption, he would pay $5,400, so the homestead exemption saves him $450 per year.
Real World Scenarios
Comparing Two Counties Before Buying
A retiree is choosing between a $400,000 home in County A with a 12-mill rate and a $400,000 home in County B with a 22-mill rate. Both assess at 100%. County A produces an annual bill of $4,800. County B produces $8,800. Over 10 years, the County B home costs $40,000 more in property tax alone. That difference can wipe out any price advantage on the home itself. Run both through the calculator before making an offer, and factor the monthly tax into your affordability check using our House Affordability Calculator.
A Reassessment That Doubles Your Bill
David bought his home in 2014 for $180,000. The market boomed, and a 2026 reassessment values it at $420,000. His millage rate stayed at 16 mills. His bill jumped from $2,880 to $6,720 in one year. Some states cap annual assessed value increases, which softens this shock. California's Proposition 13 limits increases to 2% per year until the home is sold. Michigan caps increases at 5% or the inflation rate, whichever is lower. Check whether your state has a similar cap, often called a homestead valuation cap or assessment cap.
Appealing an Over-Assessment
Linda's assessor valued her home at $500,000, but comparable sales in her neighborhood sit at $430,000. At a 20-mill rate, the over-assessment costs her $1,400 per year. She files a property tax appeal with her local board of review, presents three comparable sales, and wins a reduction to $430,000. Her new bill is $8,600 instead of $10,000. Most jurisdictions allow appeals during a specific window each year, often after the assessment notice is mailed.
Common Mistakes to Avoid
- Confusing market value with assessed value: These are different numbers. Some states assess at a fraction of market value, and caps can freeze assessed value below market value for years. Always use the assessed value on your tax bill when checking the math.
- Forgetting to apply exemptions: Homestead, senior, disability, and veteran exemptions can cut your taxable value significantly. Many homeowners never file for them. Check your assessor's website for what you qualify for.
- Adding millage rates incorrectly: Your total millage rate is the sum of county, school district, city, and special district rates. Do not use just one portion. Your tax bill lists the full breakdown.
- Ignoring escrow: If your mortgage includes an escrow account, your lender collects property tax monthly and pays the bill annually. A reassessment can trigger a shortage and a higher monthly payment. Plan for this when you see your assessment rise.
Limitations of This Calculator
This tool estimates property tax using a single millage rate and a flat exemption. It does not model split millage rates that apply differently to school versus municipal portions, percentage-based homestead exemptions, assessment caps, or special district levies. It does not account for state property tax credits or rebates. For an exact figure, use your local assessor's tax calculator or read your annual tax bill. If you are buying a home, the seller's current bill may not reflect your future bill after reassessment.
Authoritative Research and Resources
- Tax Foundation: State and Local Property Tax Collections - State-by-state comparison of average property tax burdens and effective rates, useful for comparing your bill against the national picture.
- IRS Publication 530: Tax Information for Homeowners - Explains which property tax payments are deductible on your federal return and the SALT deduction cap that limits that benefit.
For related tools, estimate your full housing cost with our Mortgage Calculator, see your net pay after all taxes with our Take-Home Paycheck Calculator, or check your federal income tax with our Income Tax Calculator.