This page explains exactly what the calculator does, what it leaves out, and where the supporting facts on this site come from. Content is reviewed by Numerlyn LLC before it is published.
Where a tax bill is built from a mill rate, the base ad valorem tax is: taxable assessed value / 1,000 x mill rate, with taxable assessed value equal to market value x assessment ratio - fixed-dollar exemption, never below zero. The Mississippi Department of Revenue states the same structure as true value x assessment ratio x millage rate, and defines one mill as 1/1,000 of a dollar.
Property value. Market or appraised value before any ratio. Negative or blank entries are treated as zero.
Assessment ratio. A percentage from 0 to 100. Values above 100 are capped at 100.
Mill rate. Dollars per $1,000 of taxable assessed value. Enter the combined rate of all taxing bodies on your bill.
Fixed-dollar exemption. A flat amount subtracted from assessed value. If it exceeds assessed value, taxable value is zero rather than negative.
The calculator shows the assessed value before and after the exemption, the estimated annual tax rounded to whole dollars, the monthly equivalent (annual divided by 12), and the tax as a share of the property value you entered. The share is a simple ratio of two numbers on your screen, not a statewide or official effective rate.
Value $285,000, ratio 100%, mill rate 18.5, exemption $0: assessed value $285,000, taxable $285,000, tax 285 x 18.5 = $5,272.50, shown as $5,273 per year and $439 per month, 1.85% of value. With a 90% ratio and a $50,000 exemption: assessed $256,500, taxable $206,500, tax 206.5 x 18.5 = $3,820.25, shown as $3,820 per year and $318 per month. These cases are built into the automated test file used before the site is published.
It does not model percentage exemptions, tax credits, circuit-breaker or deferral programs, caps or freezes on yearly increases in value, special assessments, flat fees, partial-year ownership, new-construction proration, supplemental bills after a sale, differing classes of property within one county, or late-payment penalties and discounts. Any of these can move a real bill away from the estimate. The result is labeled a base ad valorem estimate for that reason.
Values are held at full precision during the calculation and rounded only for display, to the nearest dollar. Your tax office may round at different steps, so a difference of a few dollars is normal.
Facts quoted on the site are tied to the following primary or official sources, with the year given where a figure changes over time: Mississippi Department of Revenue, Property Tax Frequently Asked Questions (assessment ratio and mill definition); Texas Comptroller, Property Tax Exemptions (homestead exemption rules); Tennessee State Board of Equalization, Value Appeals (appeal process and evidence); Tax Foundation, Property Taxes by State and County, 2024, based on U.S. Census Bureau American Community Survey tables B25082 and B25090 (effective rates); IRS Topic 503, the 2025 Schedule A instructions and Publication 505 (2026) for the SALT deduction; IRS Revenue Procedure 2025-32 for the 2026 standard deduction; and Regulation X, 12 CFR 1024.17, as summarized by the Consumer Financial Protection Bureau, for escrow accounts.
Zero or blank value. The result is $0 and the share-of-value line shows n/a, because dividing by zero has no meaning.
Exemption larger than assessed value. Taxable value stops at zero. A $150,000 exemption on a $100,000 assessed home gives $0, not a negative bill.
Mill rate of zero. The tax is $0. Some areas show a rate as a percentage; multiply it by 10 first to get mills.
Very low assessment ratios. A 10% ratio with a 120 mill rate on a $285,000 home gives assessed value $28,500 and tax 28.5 x 120 = $3,420. This is the same dollar result as a 100% ratio with a 12 mill rate, which shows why the ratio and the mill rate must be read together.
Take last year's bill. Write down the assessed value, the exemptions and each rate. Enter them. If the calculator's answer is within a few percent of the amount shown as ad valorem tax on the bill, the inputs are right. If it is far off, the difference usually comes from one of four places: the ratio, the combined rate, the exemption type, or a charge that is not value-based. Then change the value to this year's assessed value and compare against the new bill when it arrives.
A national tool cannot encode thousands of local rules without being wrong in many places. We chose a transparent method with four inputs you can read straight from your own documents, and we state clearly what is left out. A tool that shows its work lets you spot a mismatch yourself.
Rates, caps and exemptions change. Every year-specific figure on the site names its year. If you spot a figure that no longer matches the source, tell us at contactnumerlyn@gmail.com and we will review it.