Property Taxes

How Property Tax Is Calculated (With a Free Calculator)

By Aritz Boveda · Published October 21, 2026
Fact-checked against primary sources on October 21, 2026

Your property tax bill comes from four numbers: what the assessor says your home is worth, the share of that value your state taxes, any exemptions you qualify for, and the combined tax rate set by every local government that serves your address. Multiply the taxable value by the rate and you have the bill.

Annual property tax = (market value × assessment ratio − exemptions) × tax rate

The rest of this guide walks through each piece, shows two worked examples, and explains why two homes with the same price can have very different bills.

Step 1: Market value

Every assessor starts by estimating what your home would sell for. Most use mass appraisal: they compare recent sales of similar homes nearby, adjust for size, age and condition, and apply the result across thousands of properties at once. Nobody walks through your house each year.

That value is usually tied to a specific valuation date, often January 1, and may be updated every year or only every few years depending on your state. If your county reappraises every three years and prices rose sharply in between, expect a jump when the new values arrive.

Step 2: The assessment ratio

Some states tax 100% of market value. Others tax only a fixed fraction, called the assessment ratio. A home worth $300,000 in a place with a 40% ratio has an assessed value of $120,000.

A low ratio does not mean low taxes. Local governments still need the same amount of revenue, so places with low ratios usually have higher nominal rates. That is why comparing tax rates between states is misleading unless you convert them to an effective rate, the bill as a percentage of market value. The Lincoln Institute’s 50-state study uses exactly that measure for this reason.

Some states also cap how fast assessed values can rise each year for a homeowner who stays put. In those places, your assessed value can sit well below what the home would actually sell for, and a new buyer of the same house may pay much more than the previous owner did.

Step 3: Exemptions

Exemptions subtract a dollar amount (or a percentage) from the assessed value before the rate is applied. The most common is the homestead exemption for an owner-occupied primary residence. Many places add extra relief for seniors, people with disabilities and veterans.

Exemptions are rarely automatic. You typically have to file an application with the county assessor, often by a spring deadline, and some must be renewed. If you bought your home recently, check your bill: a missing homestead exemption is one of the most common and most expensive mistakes new owners make.

Step 4: The tax rate (mills)

Your bill is not set by one government. The county, the city or town, the school district and special districts (fire, library, water, parks) each levy their own rate, and they are added together.

Rates are often expressed in mills. One mill is $1 of tax per $1,000 of taxable value, or 0.1%. A combined rate of 22 mills equals 2.2%. Some places quote rates per $100 of value instead, so $2.20 per $100 is the same 2.2%.

Each body sets its rate by working backward from its budget: it decides how much revenue it needs and divides by the total taxable value in its area. When values across the area rise, rates can fall and your bill may stay roughly the same. When values rise but budgets rise faster, the bill goes up.

Worked example 1: full-value state with a homestead exemption

The exemption saves this owner $25,000 × 0.022 = $550 a year. Over ten years that is $5,500, for filling in one form.

Worked example 2: fractional assessment

The nominal rate here is more than double the first example, yet the bill is lower. Only the effective rate lets you compare the two.

Why your neighbor pays a different amount

• Different assessed values. Size, lot, condition and last sale all affect the estimate.
• Assessment caps. Long-time owners in capped states can pay far less than recent buyers.
• Exemptions. A neighbor with senior or veteran relief may pay a fraction of your bill.
• District lines. Two houses on the same street can sit in different school or fire districts.

How to check your own bill

1. Find your assessment notice or tax bill on the county assessor’s or treasurer’s website. Most let you search by address.
2. Confirm the property details: square footage, bedrooms, bathrooms and lot size. Errors here inflate values.
3. Check which exemptions are applied. If you live in the home and none are listed, ask the assessor’s office what you qualify for.
4. Enter the numbers in the calculator above and compare with your bill. A large gap usually means a special assessment or a district you didn’t account for.
5. If the market value looks too high compared with recent sales of similar homes, you can usually appeal. Deadlines are short, often 30 to 60 days after the notice is mailed.

Property tax and your mortgage payment

If you have a mortgage, your lender probably collects property tax every month through an escrow account and pays the bill for you. When your tax goes up, your monthly payment goes up at the next escrow review, even with a fixed-rate loan. Budget for that: a fixed rate fixes your interest, not your taxes.

Key takeaways

• The formula is simple: taxable value × rate. The hard part is knowing your assessment ratio, exemptions and combined rate.
• Compare places using the effective rate, never the nominal rate.
• Apply for every exemption you qualify for, and check the property details on your record.
• Your bill can change even if your rate doesn’t, because values and budgets change.