How do I find my actual assessment ratio and millage rate?

Both appear on the property tax notice or the county assessor's website, usually listed as the assessed value and the combined mill levy for your taxing districts. Search '[your county] assessor property tax rate' if the physical notice is not on hand; the ratio and rate are public record everywhere in the US.

Why did my property tax bill go up even though the rate did not change?

The taxable base moved instead of the rate. A reassessment cycle, the expiration of a temporary exemption, or a recent sale that reset the assessed value to the purchase price can all raise the bill with the millage held flat.

Is property tax the same as the escrow amount on my mortgage statement?

Not exactly. The escrow line usually bundles property tax with homeowners insurance and, in some cases, mortgage insurance, so it will run higher than the tax-only monthly figure this calculator produces.

Can I appeal my assessed value if it looks too high?

Yes, nearly every US county has a formal appeal window, typically 30 to 90 days after the assessment notice is mailed, where you can present comparable sales to argue the assessed value overstates market value. Missing the window usually means waiting for the next assessment cycle.

Is property tax deductible on federal income tax?

It can be, as part of itemized deductions on Schedule A, but the combined state and local tax deduction is capped, which limits how much of a large property tax bill actually reduces federal taxable income for homeowners in high-tax areas.

Do renters pay property tax indirectly?

Landlords generally build the property tax into the rent they charge rather than absorbing it, so a rate increase on a rental property tends to show up in the next lease renewal rather than as a separate line item on a tenant's bill.

Property tax calculator

This calculator turns a home's market value into the yearly bill a county or municipality actually sends: multiply the assessed value by the local rate, subtract any exemption first, and split the total into a monthly escrow figure. The result is only as good as the assessment ratio and millage rate you enter, because both are set locally and change on their own schedule.

Reading the assessed value line

Few jurisdictions tax the full market value. Assessors apply an assessment ratio first, so a 300,000 home in a county that assesses at 80% of value produces an assessed value of 240,000 before any rate is applied. Skipping this step is the most common reason a homeowner's own back-of-envelope estimate is wrong by 20% or more.

A homestead or senior exemption then reduces that assessed figure directly, dollar for dollar, before the rate is applied. A 25,000 exemption on a 425,000 assessed value drops the taxable base to 400,000, which is worth more to an owner in a high-rate area than the same exemption is worth in a low-rate one.

Once you have the taxable base, the rate — quoted as a millage (dollars per 1,000 of value) or as a straight percentage — produces the bill. A rate of 1.1% and a rate of 11 mills are the same thing written two different ways, and mixing them up is the second most common input error.

Three worked bills

A 300,000 home assessed at 80% of value with a 1.25% rate and no exemption: assessed value is 240,000, so the yearly tax is 3,000, or 250 a month in escrow. That is an effective rate of exactly 1.0% of market value, a useful shorthand once you have run a few of these.

A 450,000 home assessed at full value (100%) with a 25,000 homestead exemption and a lower 0.9% rate: the taxable base is 425,000, giving a yearly bill of 3,825, or about 319 a month. Despite the higher market value, the effective rate on market value works out to 0.85%, below the first example, because the assessment ratio and exemption matter as much as the sticker rate.

Same 350,000 home, same 60% assessment ratio, but the local rate rises from 1.0% to 1.3% after a school bond passes: assessed value stays at 210,000, so the bill moves from 2,100 to 2,730, a jump of 630 a year or 52.50 a month. That is the size of a rate increase most homeowners never see itemized until the notice arrives.

Why the number on the notice can differ from this one

This formula assumes the assessed value on file is current. Most counties reassess on a cycle of one, three, or even six years, so a home that has appreciated since the last reassessment is still being taxed on the old, lower figure until the next cycle catches up, at which point the bill can jump well past what a simple year-over-year trend would predict.

It also assumes a single flat rate, but many bills are actually the sum of several overlapping levies: county, school district, municipal, fire district and special assessments, each set independently and each capable of changing in a different year. Treat the rate entered here as the combined millage, not any single line item, or the total will understate the real bill.

Recent purchases are a special case. Several states reassess a property to its sale price the year after closing, so a buyer who pays above the prior assessed value should expect the first full bill to be noticeably higher than the seller's last one, even with no rate change at all.

Jurisdiction and timing differences

In the United States, assessment ratios, exemption rules and reassessment cycles are all set at the state or county level, so there is no single national formula; California's Proposition 13 caps annual assessed-value growth at 2% until a sale resets it, while many other states reassess more freely, producing very different trajectories for two identical homes in different states.

Escrowed borrowers should also expect a true-up. Lenders estimate the annual property tax when they set the monthly escrow payment, and an escrow analysis once a year corrects any shortfall or surplus, which is why a mortgage payment can shift even when the rate on the loan itself has not changed.

Outside the US, most residential property taxes work on a different base entirely, such as the UK's council tax bands tied to a fixed 1991 valuation rather than current market value, so this market-value-times-rate formula does not translate directly to a UK council tax bill.

Frequently asked questions

How do I find my actual assessment ratio and millage rate?: Both appear on the property tax notice or the county assessor's website, usually listed as the assessed value and the combined mill levy for your taxing districts. Search '[your county] assessor property tax rate' if the physical notice is not on hand; the ratio and rate are public record everywhere in the US.
Why did my property tax bill go up even though the rate did not change?: The taxable base moved instead of the rate. A reassessment cycle, the expiration of a temporary exemption, or a recent sale that reset the assessed value to the purchase price can all raise the bill with the millage held flat.
Is property tax the same as the escrow amount on my mortgage statement?: Not exactly. The escrow line usually bundles property tax with homeowners insurance and, in some cases, mortgage insurance, so it will run higher than the tax-only monthly figure this calculator produces.
Can I appeal my assessed value if it looks too high?: Yes, nearly every US county has a formal appeal window, typically 30 to 90 days after the assessment notice is mailed, where you can present comparable sales to argue the assessed value overstates market value. Missing the window usually means waiting for the next assessment cycle.
Is property tax deductible on federal income tax?: It can be, as part of itemized deductions on Schedule A, but the combined state and local tax deduction is capped, which limits how much of a large property tax bill actually reduces federal taxable income for homeowners in high-tax areas.
Do renters pay property tax indirectly?: Landlords generally build the property tax into the rent they charge rather than absorbing it, so a rate increase on a rental property tends to show up in the next lease renewal rather than as a separate line item on a tenant's bill.

Sources

IRS Topic no. 503, Deductible taxes — Confirms the state and local tax (SALT) itemized deduction, which includes property tax, remains capped for individual filers as of the 2025 tax year guidance.
US Census Bureau, ACS Table B25103 — Publishes median real estate taxes paid by owner-occupied households by mortgage status, updated annually with each new American Community Survey release (2022 1-year estimates shown).