How Property Tax Is Calculated

Published: 2026-07-12 | Updated: 2026-07-12

Disclaimer: This article provides general educational information based on publicly available data. Property tax rules vary by state, county, and city. Confirm figures with your local tax assessor's office and a qualified tax professional before making decisions.

Most homeowners pay their property tax bill twice a year without ever seeing the math behind it. Understanding the calculation is the first step to challenging an unfair assessment, estimating a future move, or simply knowing where your money goes. The good news: the core formula is simple. The challenge is that every state applies different inputs, so the same house can produce very different bills depending on local rules.

The core formula is:

Property Tax = (Assessed Value − Exemptions) × Tax Rate (millage)

Every term in that equation is shaped by state and local law. Below we walk through each step, with examples, so you can follow your own bill line by line.

Step 1: Determine Market Value

Your local assessor estimates your property's market value — what it would sell for in an open market. Common methods include the sales comparison approach (recent sales of similar nearby homes), the cost approach (replacement cost minus depreciation), and the income approach (for rental or investment property, based on expected income). Most residential assessments rely on sales comparison within the neighborhood, which is why a wave of high sales can push nearby assessments up even if you have not sold.

Step 2: Apply the Assessment Ratio

Many states do not tax 100% of market value. They apply an assessment ratio (for example, 10%, 33%, or 100%, depending on state law). The result is the assessed value. Example: a home with $300,000 market value in a state with a 10% assessment ratio has an assessed value of $30,000 — not $300,000. This is why nominal rates look high in some states but effective rates stay low. The assessment ratio is one of the least-understood but most important drivers of your bill.

Step 3: Subtract Exemptions

Exemptions reduce the taxable value before the rate is applied:

Exemptions are the homeowner's single biggest lever, and they are frequently left unclaimed. If you own and occupy your home, check your county's exemption list every year.

Step 4: Apply the Millage (Tax) Rate

The millage rate is set by local taxing authorities — county, city, school district, and special districts. One "mill" equals $1 of tax per $1,000 of assessed value. Example: if your taxable value is $250,000 and the combined millage is 20 mills, your tax = $250,000 × 0.020 = $5,000. In practice, your bill is the sum of multiple levies. A typical Texas bill layers school district, county, city, hospital district, and community college rates. See our millage rate guide for the full breakdown. The school district portion is usually the largest and the most contested at budget time.

Step 5: Assessment Caps & Limits

Several states cap how fast assessed value can rise:

These caps protect long-time owners but mean new buyers pay sharply more than neighbors — a key reason two identical homes can have very different bills.

Equalization & Appeals

Some states use an equalization rate to harmonize assessments across localities so that similarly valued homes pay similar taxes regardless of which town assessed them. If your assessment looks too high relative to recent comparable sales, you generally have the right to appeal to a local board of review. Successful appeals are common when the homeowner presents clear market evidence. This is one of the highest-leverage ways to lower a bill without moving, and the filing fee is usually modest.

Commercial vs. Residential

Many states assess commercial and residential property differently — often taxing commercial property at a higher ratio or without the caps that protect homeowners. That is why a small business owner's tax bill can rise faster than a neighbor's home even on similar market values. If you own a mixed-use or rental property, expect different treatment and plan accordingly.

Worked Example

Scenario: A $350,000 home in a state with 100% assessment, a $25,000 homestead exemption, and a 1.20% effective rate.

Taxable value = $350,000 − $25,000 = $325,000

Tax = $325,000 × 0.012 = $3,900/year

Without the exemption, the bill would be $4,200 — the exemption saves $300/year, or $9,000 over 30 years.

Frequently Asked Questions

Why is my assessed value lower than my sale price?

Many states assess at a ratio below 100% of market value, or cap annual increases (Prop 13, Save Our Homes). Your assessment reflects the state's formula, not necessarily today's market price.

Who sets the tax rate?

Local governments — school boards, county commissions, city councils — set millage each budget cycle, subject to state caps and voter-approved bonds.

Can I appeal if my home value dropped?

Yes. If market value falls below your current assessed value, most assessors will reduce the assessment on request or automatically during a reassessment cycle.

Calculate Your Own Bill

Use our free property tax calculator to plug in your home value, state, and exemptions and see your estimated annual tax. It applies your state's real parameters and shows the impact of each exemption.

Related Resources

Understanding Millage: Where the Rate Comes From

The single number on your bill is the sum of many smaller levies, each set by a different authority. A typical combined rate might look like this: school district 12 mills, county 3 mills, city 4 mills, hospital district 1 mill, and community college 1.5 mills — a total of 21.5 mills, or 2.15% of assessed value. Each authority proposes its levy during budget season, and in many states voters must approve bonds or overrides above a certain threshold. That is why attending a school-board or county-budget meeting, or voting in a millage referendum, directly changes your tax bill. The school portion is usually the largest single piece and the most frequent source of annual increases.

Assessment Timing: When Your Value Is Set

When your assessed value is established matters as much as the rate. States fall into a few patterns:

Knowing your state's pattern tells you whether to expect a steady climb, a sudden jump at revaluation, or stability until you sell. It also tells you when appeals are most worthwhile.

A Second Worked Example (Low-Ratio State)

Scenario: A $300,000 home in a state that assesses at 10% of market value, with a $10,000 homestead exemption, and a combined millage of 80 mills (8%).

Assessed value = $300,000 × 10% = $30,000

Taxable value = $30,000 − $10,000 = $20,000

Tax = $20,000 × 0.08 = $1,600/year

Notice the 8% millage looks high, but because the assessment ratio is only 10%, the effective rate is just 0.53%. This is exactly why you must look at the effective rate, not the nominal millage.

How to Appeal Your Assessment

If your assessed value exceeds what your home would sell for, you are overpaying. The appeal process is more approachable than most homeowners expect:

  1. Request your assessment record from the assessor and check it for errors (wrong square footage, extra bathrooms, wrong lot size).
  2. Collect 3–5 recent sales of comparable homes nearby that sold for less than your assessment implies.
  3. File the appeal form by the deadline (often 30–60 days after the assessment notice).
  4. Present your evidence at the board of review; be factual and brief.
  5. If denied, consider the next level (state tax commission) for large differences.

Many homeowners who appeal win at least a partial reduction, and the savings recur every year until the next reassessment. The only real cost is your time.

Using Our Calculator for Planning

Our free property tax calculator lets you test scenarios without touching the math by hand. Enter your home value, pick your state, and add exemptions; it returns an estimated annual bill and shows how each exemption moves the number. Use it to compare two homes, model a future move, or see the impact of a homestead exemption you have not yet filed. For county-level precision, pair the estimate with the millage posted on your county assessor's website.

Common Calculation Mistakes

Property Tax and Your Mortgage Escrow

Most homeowners do not write a property-tax check directly. Instead, the lender collects one-twelfth of the annual tax (plus insurance) each month into an escrow account and pays the taxing authority when bills come due. This is why your monthly "mortgage payment" is really PITI: principal, interest, taxes, and insurance. If your assessed value rises, your escrow shortfall grows and the lender raises your monthly payment — sometimes mid-year — to cover it. Understanding this link explains why a surprise assessment shows up as a higher mortgage bill, not a separate tax notice.

Annual vs. Semiannual Payments

Many states bill property tax in two installments (e.g., November and the following January or February). Some offer a small discount for paying the full year early, and most charge penalties plus interest for late payment. If you escrow, the lender handles timing; if you pay directly, mark both due dates and watch for the penalty cliff. Setting aside the funds monthly, even outside escrow, avoids a painful lump sum and keeps your standing with the taxing authority clean.

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