How to use the property tax calculator
- Enter the market value. Use the assessor’s market value from your latest notice, or what the home would sell for.
- Enter the assessment ratio. Leave it at 100% if your area taxes full market value. Some states assess only a fixed share, for example 40% or 10% of market value for homes.
- Choose how the rate is quoted and enter it: as a percent, or in mills per $1,000 of value. Use the total of every taxing body that appears on the bill.
- Enter exemptions in dollars, such as a homestead, senior or veteran exemption. Leave it at 0 if none apply.
The first table shows the tax at market values up to 20% higher or lower; the second shows the same home at other common rates.
The formula
Taxable value = Assessed value − Exemptions
Annual tax = Taxable value × Tax rate
Effective rate = Annual tax ÷ Market valueA rate in mills is divided by 1,000: 11 mills = 0.011 = 1.1% of taxable value.
A worked example
A home has a market value of $400,000 and is assessed at 100%, so its assessed value is $400,000. The owner’s $25,000 homestead exemption brings the taxable value to $375,000.
At a combined rate of 1.1%, or 11.00 mills, the annual tax is $4,125.00, or $343.75 a month. The effective rate on market value is 1.03%, and the exemption saves $275 a year compared with $4,400.00 without it.
Mills, ratios and why rates are hard to compare
Tax rates look very different from place to place even when bills are similar, because the rate always applies to the taxable value and the rules for reaching it differ. A county that assesses homes at 40% of market value needs a much higher rate to raise the same revenue as one that assesses at 100%.
| Assessed at 100% | Assessed at 40% | |
|---|---|---|
| Rate | 11.00 mills | 27.5 mills |
| Taxable value | $375,000 | $135,000 |
| Annual tax | $4,125.00 | $3,712.50 |
| Effective rate | 1.03% | 0.93% |
The rate in the second column is two and a half times higher, yet the bill is lower: the same dollar exemption removes a bigger share of a smaller assessed value. This is why the effective rate, tax divided by market value, is the fair way to compare one home or one town with another.
Reassessment and caps
Assessors revalue property on a schedule that varies by state, from every year to every several years. When values rise, the assessed value follows and so does the bill, unless the taxing bodies lower their rates. Rates themselves are set each year from local budgets, so a bill can rise even without a new assessment.
Many states limit how fast assessments or tax bills on homes can grow. The best-known example is California’s Proposition 13, which sets the basic rate at 1% of assessed value and caps increases in assessed value at 2% a year until the property changes hands, when it is reassessed at the purchase price. Other states use different caps, often only for owner-occupied homes. Under a cap, two identical neighboring homes can pay very different taxes, and a buyer’s bill can be far higher than the seller’s was. Always estimate tax from the price you will pay, not from the seller’s current bill.
What this calculator does not include
The calculator applies one combined rate to one taxable value. Real bills can include flat fees and special assessments (for sewers, lighting or bonds) that do not depend on value, exemptions calculated as a percentage rather than a dollar amount, and different rates for land and buildings. Some places also offer credits or deferrals for seniors or lower-income owners. Your county assessor or treasurer has the exact rules and the official figures.