Property tax is the single largest recurring cost of owning a home that never appears on your mortgage statement's principal-and-interest line. It is levied annually by your county, school district, and municipal government, and it can easily add thousands of dollars a year to your housing budget. This free property tax calculator takes your home's market value, the local assessment ratio, and the combined millage rate, and returns the annual and monthly tax bill along with your effective rate — so you can compare counties, estimate escrow, and avoid sticker shock at closing.
Unlike an income tax, which is calculated on what you earn, property tax is an ad-valorem tax: it is calculated on what your property is worth. That means the number hinges on three independent choices the local government makes for you — the assessed value, the assessment ratio, and the millage rate — and this tool lets you adjust all three.
How to Use
- Enter the Home Market Value — what a buyer would reasonably pay for the property today. Your county assessor publishes this figure on the tax bill, but you can also use the purchase price or a recent appraisal.
- Set the Assessment Ratio. Most jurisdictions do not tax 100% of market value; common ratios are 80%, 90%, or 100%. If your county bills you on 80% of value, enter 80.
- Type the Millage Rate as a percent per year. One mill equals $1 of tax per $1,000 of assessed value, or 0.1%. A combined rate of 12 mills is therefore 1.2%. Find the total on your most recent tax statement — it usually stacks county, school, and city mills.
- Add a Homestead / Exemption if you qualify. Many states subtract a fixed dollar amount (often $5,000–$50,000) from the assessed value for owner-occupants before applying the levy.
- Read the result card. The Annual Property Tax is what the county will bill you each year; the Monthly Property Tax is what you should be setting aside (or what your lender will collect in escrow); and the Effective Rate shows the tax as a percentage of actual market value, which is the fairest way to compare locations.
The math is deliberately transparent: assessed value equals market value times the assessment ratio; taxable value subtracts any exemption; the annual tax is taxable value times the millage rate divided by 100.
How Property Tax Is Actually Calculated
The formula used by every county assessor in the United States is the same:
Annual Tax = (Market Value × Assessment Ratio − Exemption) × Millage Rate
Worked example on a $300,000 home in a county that assesses at 80% and charges 1.2%:
- Assessed value = $300,000 × 80% = $240,000
- Taxable value (no exemption) = $240,000
- Annual tax = $240,000 × 1.2% = $2,880 per year
- Monthly escrow = $2,880 ÷ 12 = $240 per month
- Effective rate = $2,880 ÷ $300,000 = 0.96% of market value
Notice that the stated millage rate (1.2%) and the effective rate (0.96%) are different numbers. The gap exists because the county only taxes 80% of the home's value. When you compare two towns by their advertised millage, always compare the effective rate instead — a place that taxes 100% of value at 1.0% costs more than a place that taxes 80% at 1.2%.
A "mill" is simply a unit: one mill means one dollar of tax per thousand dollars of assessed value. So 12 mills equals 1.2%, 25 mills equals 2.5%, and 50 mills equals 5%. Many older tax bills still print millage in mills rather than percent, so the conversion matters.
What Drives the Bill Up or Down
Three levers move your property tax, and only one of them is yours:
- Assessed value. When the county reappraises your home, the assessed value rises — usually capped at 1–2% per year in states like California (Prop 13) and Florida (Save Our Homes), but uncapped elsewhere.
- Assessment ratio. Some states mandate a uniform ratio (e.g. West Virginia at 60%); others let each county choose.
- Millage rate. School districts are the biggest swing factor. A vote to fund a new school building can add 5–10 mills overnight, raising a $300,000 home's bill by $1,200–$2,400 a year.
Exemptions are the homeowner's lever. Homestead caps, senior freezes, veteran exemptions, and disability exemptions all subtract from the taxable value, and they are applied before the millage — which means a $50,000 exemption at 1.2% saves exactly $600 a year, no matter how high the value climbs.
Examples
Example 1 — The benchmark household. A family owns a $300,000 home in a county that assesses at 80% and levies 1.2%. Their assessed value is $240,000, the annual tax is $2,880, and the monthly escrow deposit is $240. Their lender collects $240 each month and pays the county on their behalf.
Example 2 — The $50,000 homestead exemption. The same household qualifies for a Florida-style homestead exemption. Taxable value drops from $240,000 to $190,000, the annual tax falls to $2,280, and the monthly escrow drops to $190 — a $50 per month saving that compounds over the life of the mortgage.
Example 3 — The million-dollar comparison. On a $1,000,000 home assessed at 100% with a 1.2% millage, the annual tax is $12,000 and the monthly escrow is $1,000. Comparing that to a nearby county that advertises 1.5% on an 80% assessment: taxable value is $800,000 and the tax is $12,000 as well — the same dollar bill, even though the advertised rate looks 25% higher. This is why the effective rate line on this calculator matters.
Example 4 — School-bond shock. A school district passes a $200 million bond, adding 8 mills (0.8%) to the rate. On the original $300,000 home, the extra levy raises the annual tax from $2,880 to $4,800 — a $1,920 increase, or $160 more per month.
FAQ
How is property tax calculated?
Property tax is an ad-valorem levy: the county multiplies your home's market value by the local assessment ratio to get an assessed value, subtracts any exemptions, and then multiplies by the millage rate (expressed as a percent). On a $300,000 home assessed at 80% with a 1.2% rate, the math is $300,000 × 0.80 × 0.012 = $2,880 per year.
What is a millage rate and how do I convert it to a percent?
One mill equals $1 of tax per $1,000 of assessed value, which is 0.1%. To convert mills to a percent, divide by 10: 12 mills = 1.2%, 25 mills = 2.5%, 50 mills = 5%. Many tax bills print the rate in mills, but this calculator asks for percent so the arithmetic is direct.
What is the assessment ratio and why does it matter?
The assessment ratio is the share of your home's market value that the county actually taxes. A 100% ratio means every dollar of market value is taxed; an 80% ratio means only 80 cents on the dollar is taxed. This is why two jurisdictions with the same advertised millage can charge very different real bills — the lower ratio functions as an automatic across-the-board exemption.
What is a homestead exemption and how much does it save?
A homestead exemption subtracts a fixed dollar amount (commonly $5,000–$50,000) from the assessed value for owner-occupied homes before the millage is applied. At a 1.2% rate, a $50,000 exemption saves $600 a year ($50/month). It does not reduce the assessed value itself — it only lowers the taxable base.
Why is my effective rate different from the millage rate?
The millage rate applies to the assessed value, while the effective rate applies to the actual market value. Because the assessment ratio is usually below 100%, the effective rate is always lower than the millage. On a $300,000 home taxed at 1.2% on an 80% assessment, the millage is 1.2% but the effective rate is 0.96%. Comparing effective rates across counties is the only apples-to-apples way to compare tax burden.
Do I pay property tax every month?
You do not send a monthly check to the county, but if you have a mortgage your lender almost certainly collects one-twelfth of the estimated annual tax each month into an escrow account and pays the county when the bill comes due. The monthly figure on this calculator matches that escrow line. If you own the home outright, you will typically pay once or twice a year directly to the treasurer.
How can I lower my property tax bill?
The three practical levers are: (1) file for every exemption you qualify for — homestead, senior, veteran, disability; (2) appeal the assessed value if recent comparable sales suggest it is too high; and (3) vote carefully on school and municipal bond referenda, because the millage rate is set directly by those ballots. This calculator does not give tax advice, but it lets you model each lever before you act.
Disclaimer
This property tax calculator is provided for informational purposes only and does not constitute financial, tax, or legal advice. Estimates are based on the inputs you enter and the standard ad-valorem formula; actual bills vary by county, school district, state law, exemptions, appeal outcomes, and voter-approved bonds. Always confirm your exact millage rate, assessment ratio, and qualifying exemptions directly with your county assessor's office before making financial decisions.