Property tax questions fall into two groups: what the terms mean, and why an estimate does not match a real bill. The answers below cover both in plain language. Rules are set locally, so where an answer depends on your state or county, it says so. Where figures are quoted, the source and year are named.
What is a mill rate? +
A mill rate, also called a millage rate, is the amount of tax per $1,000 of taxable assessed value. One mill is one-thousandth of a dollar, so 18.5 mills means $18.50 per $1,000. The Mississippi Department of Revenue describes a mill the same way. Most bills combine rates from the county, city or township, school district and any special districts.
Is a mill rate the same as a percentage rate? +
They are two ways to write the same idea. Multiply a percentage by 10 to get mills: 1.85% is 18.5 mills. Divide mills by 10 to get a percentage. Just make sure the rate applies to the same base (assessed value or market value) that you use in the calculator.
What is assessed value, and how is it different from market value? +
Market value is roughly what a willing buyer would pay. Assessed value is the figure your local assessor uses to tax the property. In some places the two are equal, and in others assessed value is a set percentage of market value, called the assessment ratio. Check your assessment notice to see which applies.
What is an assessment ratio? +
It is the percentage of market value that is treated as taxable assessed value. A 100% ratio means no reduction. A 10% ratio, as Mississippi uses for owner-occupied single-family homes, means a $285,000 home has an assessed value of $28,500, and the mill rate is correspondingly much higher.
What is a homestead exemption, and is it automatic? +
A homestead exemption lowers the taxable value of an owner-occupied primary residence. Some are fixed dollar amounts, some are percentages, and some work as credits. Whether you need to apply depends on the state. The Texas Comptroller says an owner must apply for an exemption in most circumstances, so do not assume yours was applied without checking your notice.
Why does the calculator ask for a fixed-dollar exemption only? +
Because a fixed amount removed from assessed value is the one exemption type that fits the mill-rate formula cleanly. Percentage exemptions, credits and caps depend on local rules the tool cannot know. If you have one, estimate its effect separately or enter an approximate dollar equivalent.
Why does my estimate not match my actual bill? +
The usual reasons are an assessment ratio that was not applied, a mill rate that is out of date or incomplete, an exemption that was assumed but not granted, a special assessment or flat fee on the bill, a credit or cap, or a new reassessment. Compare the estimate with each line of the bill to find the gap.
How often is my property reassessed? +
It varies by state and sometimes by county. Some places reassess every year, others on a multi-year cycle. After a long gap, a large increase in assessed value can arrive all at once. Your assessor can tell you the schedule.
Can my tax rise if the mill rate stays the same? +
Yes. If your assessed value goes up through reassessment, a renovation or a change in ratio, the tax rises even with an unchanged rate. For example, on a 18.5 mill rate, a rise in assessed value from $285,000 to $342,000 adds $1,054.50 a year.
Can my tax change if my value stays the same? +
Yes. Local governments adjust rates when they set budgets, and voters can approve levies. One extra mill on a $285,000 assessed value is $285 per year.
What is an effective property tax rate? +
It is the tax actually paid divided by the home value, which makes places with different ratios and mill rates comparable. In 2024 the Tax Foundation reported statewide effective rates for owner-occupied housing from about 0.29% in Hawaii to about 1.88% in New Jersey and Illinois, using Census Bureau survey data. County and city rates vary within each state.
Should I budget with the annual or monthly figure? +
The calculator shows both. With a mortgage escrow account, your lender typically collects a monthly share and pays the bill for you. Without escrow, set aside the monthly figure so a large payment on the due date is not a surprise.
What should I do if I think my assessment is too high? +
Check the record for factual errors, work out the market value implied by your assessed value and ratio, collect recent comparable sales, find your appeal deadline right away, and follow your local process. Our guide on how to appeal walks through the steps.
Can I deduct property tax on my federal return? +
Possibly, if you itemize. Real estate taxes count toward the federal state and local tax (SALT) deduction, which is capped. For tax year 2025 the IRS lists a $40,000 cap, and Publication 505 for 2026 lists $40,400. Our SALT guide explains the details and a worked example.
Does the calculator include special assessments or fees? +
No. Special assessments, improvement districts and flat fees are billed separately and are not part of a mill-rate calculation. Add them from your bill if you want a full-bill estimate.
Is my data stored anywhere? +
No. The calculation runs in your browser and the numbers you type are not sent to us or saved. Closing or refreshing the page clears them. See the Privacy Policy for how the site itself works.
Is this tax advice? +
No. The site gives general education and estimates. For decisions about appeals, deductions or exemptions, talk to your local assessor or a qualified tax professional.