The median American homeowner paid $3,018 in property taxes in 2024, according to U.S. Census Bureau ACS data. In New Jersey, that figure reached $9,590. In Autauga County, Alabama, it was $627. Same formula, wildly different results — because the inputs depend entirely on where you live.

The formula itself takes about five seconds to run. The harder part is knowing which numbers go into it, and understanding that local governments — not the IRS, not any federal agency — set each input independently.

I went through materials from the IRS, the U.S. Census Bureau, the Tax Foundation, the Lincoln Institute of Land Policy, and several state revenue departments — including Montana, Georgia, and South Carolina — to pull together what official sources actually say about each step.

Property taxes use one formula across every US jurisdiction — (Assessed Value × Millage Rate) ÷ 1,000 — but each local input varies independently. Your assessed value comes from your home’s market value multiplied by an assessment ratio that ranges from 4% to 45%, per state revenue departments. Two homes priced identically can carry very different annual tax bills because of that ratio alone.

How Are Property Taxes Calculated Step by Step?

Property taxes follow one baseline formula across every US jurisdiction, but the inputs — assessment ratio, assessed value, and mill rate — are all set locally, which is why homes with identical market values produce such different bills. What changes from county to county are the numbers that go into the formula, not the formula’s structure.

Why the Assessment Ratio Determines Most of Your Bill

In that example, a $400,000 home with a 20% assessment ratio produces an $80,000 assessed value. At 30 mills, the annual tax comes to $2,400. Change the assessment ratio to 4% — South Carolina’s residential rate, per the South Carolina Department of Revenue — and the same $400,000 home produces a $16,000 assessed value and a $480 annual tax at the same mill rate. Same market value, same mill rate, dramatically different bill. The assessment ratio does most of the heavy lifting.

Research from the Montana Department of Revenue and Georgia Department of Revenue confirms this baseline definition: one mill equals $1 of tax per $1,000 of assessed value. That structure holds across states even when surrounding rules differ significantly.

What Is Assessed Value Versus Market Value?

Most property-tax confusion starts with one misunderstanding: assessed value is not what your home would sell for today, and in many jurisdictions the gap between them is intentional. Market value reflects what a buyer would pay in current conditions. Assessed value is what your local government uses in the tax formula after applying a jurisdiction-specific ratio to that market value.

That ratio can shrink the taxable base dramatically. A home worth $400,000 on the open market might carry an assessed value of $16,000 in South Carolina or $180,000 in certain New York City property classes — because the assessment ratios differ, not the homes.

The difference matters because assessed value feeds directly into the formula. A home assessed at $16,000 and one assessed at $180,000 generate very different tax bills even at the same mill rate.

How Assessment Caps Affect Long-Term Owners

Some jurisdictions cap how fast assessed value can rise from year to year. New York City limits Class 1 residential property increases to 6% annually and Class 2 cooperatives and condominiums to 8%, according to the NYC Department of Finance. Those caps can create a widening gap between market value and assessed value over time — benefiting long-term owners, but creating unexpectedly large bill changes when a property sells or is reassessed.

Research published in the Harvard Journal on Legislation flags a systematic pattern across many US jurisdictions: lower-value properties tend to be over-assessed relative to their market value, while higher-value properties are under-assessed. The researchers identify this as a distributional concern — the tax burden can fall disproportionately on lower-income homeowners in jurisdictions where this pattern exists.

What Is a Mill Rate or Millage Rate?

The millage rate converts assessed value into a dollar amount — one mill equals $1 of property tax for every $1,000 of assessed value, a definition confirmed by the Montana Department of Revenue and the Georgia Department of Revenue. That definition holds consistently across state materials even when the surrounding rules vary.

At 10 mills, a $100,000 assessed value produces $1,000 in property tax. At 20 mills, $2,000. At 30 mills, $3,000. The relationship is linear, but the millage rate isn’t fixed. Local taxing authorities adjust it based on annual budget needs. A homeowner whose property value hasn’t changed can still see a higher tax bill if the rate rises. Those two variables — assessed value and millage rate — move independently of each other and independently of what the home is worth on the open market.

The Tax Foundation’s 2026 analysis adds national context. Property taxes represented 28.9% of total state and local tax collections in fiscal year 2023, and 70.0% of local tax collections specifically. That level of local dependence explains why millage rates respond to local budget pressures: for most local governments, property tax is the primary revenue source.

The mini calculator below shows how your annual property tax amount translates into a monthly housing-payment impact. For example, the $2,400 annual tax from the 30-mill scenario above adds $200 per month to your PITI. Enter your own assessed value and rate to see what your local inputs produce.

Why Did My Property Taxes Go Up?

A property-tax bill can rise because of a higher assessed value, a higher millage rate, or a lapsed exemption — and any one of those can happen without any action on the homeowner’s part. Only one of those inputs is directly tied to what a home would sell for.

A new appraisal can raise your assessed value, which pushes the formula result higher. A local government can raise the millage rate to fund budget needs, which also raises the result — even when your assessed value stayed flat. An exemption that was reducing your taxable value can lapse if it wasn’t renewed or if a qualifying condition changed.

Assessment Cycles and Exemption Lapses

Assessment timing adds another layer. Most jurisdictions reassess properties on a cycle — annually, every few years, or after a sale. If your county last appraised your home three years ago and local prices have risen since, a new assessment can reflect a jump that wasn’t visible on previous bills.

Research on property-tax appeals notes that homestead, senior, and veteran exemptions aren’t always renewed automatically. Missing a renewal deadline or failing to reapply after a move can cause an exemption to lapse and increase taxable value, even when the property itself hasn’t changed.

The Census Bureau’s 2024 ACS data shows how wide that range can run: from $627 in Autauga County, Alabama, to $9,590 in New Jersey — all under the same formula. Identifying which input drove your specific change — assessed value, millage rate, or exemption lapse — is the first step in evaluating whether the bill is accurate.

Are Property Taxes Included in My Mortgage Payment?

For most homeowners with a mortgage, property taxes appear in the monthly payment through an escrow account managed by the mortgage servicer — they don’t go directly from you to the county. The monthly payment follows the PITI structure: principal, interest, taxes, and insurance.

The taxes portion represents approximately one-twelfth of the estimated annual tax bill. At the $3,018 national median, that tax contribution alone adds about $251.50 per month to the housing payment before other costs.

IRS Publication 530 draws an important distinction that affects the federal deduction. Money deposited into a mortgage escrow account isn’t the same as property taxes paid to the taxing authority. For deduction purposes, only the amount actually disbursed from escrow and paid to the local tax collector counts. The deposit date and the payment date are two separate events under IRS rules.

Use the Mortgage Calculator to See the Full PITI Picture

Entering your actual property tax amount into SaveXpert’s Mortgage Calculator shows exactly how that cost affects your full monthly PITI payment. The calculator adds it alongside principal, interest, and insurance automatically.

What this shows: The SaveXpert Mortgage Calculator lets you enter your estimated annual property tax to see its monthly contribution to your full PITI payment. The interface breaks out principal, interest, taxes, and insurance separately, with a payment breakdown chart and amortization schedule.

Are Property Taxes Tax Deductible?

Property taxes can qualify for a federal SALT deduction, but the rules changed significantly in 2025, and not every charge on a property-tax bill qualifies. The deduction is only available to taxpayers who itemize on Schedule A — and the 2025 update raised the combined SALT cap substantially from the prior $10,000 limit.

For tax year 2025, IRS Publication 530 cites a SALT deduction limit of $40,000 for individual filers and $20,000 for married taxpayers filing separately. This combined limit covers state and local income taxes, sales taxes, and property taxes together — not property taxes alone. The increase came from the One Big Beautiful Bill Act, according to Congressional Research Service materials.

The phaseout matters for higher-income filers. The deduction begins to reduce above $500,000 in modified adjusted gross income ($250,000 for married filing separately), and cannot fall below $10,000 for most individual filers under current rules.

What Qualifies and What Doesn’t

Not every charge on a property-tax bill qualifies as a deductible real-estate tax. The IRS requires that the tax apply uniformly to real property and that proceeds support general governmental purposes. Charges that generally don’t qualify include water and trash fees, HOA assessments, transfer taxes, and local improvement assessments that increase property value. These distinctions appear in IRS Tax Topic 503 and Publication 530.

What Research Shows About Property Tax Appeals and Assessment Outcomes

Research from the Lincoln Institute and Tax Foundation identifies three findings that directly affect what homeowners pay and what they can do when a bill looks wrong. After going through the Census Bureau, IRS, and state revenue department materials, several practical patterns emerged.

Realistic Expectations

Property-tax calculations can look simple while the underlying inputs vary significantly. A homeowner can face very different results because assessment ratios, assessed values, exemptions, and millage rates are all set independently by local governments and can change independently year to year. Research also shows that appeals operate on fixed deadlines — often tied to the assessment notice, not the final tax bill. Getting the formula right requires the right local inputs, and confirming those inputs typically means going directly to your county assessor rather than any federal source.

The Bottom Line: 5-Step Action Plan

The baseline property-tax formula takes five seconds to run, but getting accurate inputs requires going directly to your county assessor — every local input is set independently and isn’t available from any federal source. Here’s the research-backed sequence: