Property Tax Increase Calculator
Last year's assessment and rate, and this year's
Your result will appear here
Fill in the fields on the left and this updates as you type.
Know what this estimate is based on
- Jurisdiction
- General mathematical model
- Scope and limitations
- Educational estimate only. Confirm the assumptions, current rules, fees, and rounding that apply to your situation before making a decision.
- Source links checked
- Jul 30, 2026
Built and regression-tested by Smart Tools Lab. It has not been individually reviewed by a licensed financial, tax, or legal professional.
How to use
- 01
Find last year's assessed value on last year's tax bill or assessment notice, before exemptions, and this year's value on the new notice.
- 02
Enter your state's assessment cap as a percentage a year if one applies to your home, or 0 if not. California's Prop 13 limits increases to 2%; Florida's Save Our Homes limits a homestead to 2.7% for 2026.
- 03
Enter the exemptions taken off your assessed value, such as a homestead exemption, from the notice.
- 04
Enter last year's and this year's total tax rates in mills, the dollars of tax per $1,000 of taxable value, adding every taxing body on the bill. A percentage rate converts to mills by multiplying by 10.
- 05
Read the new bill, the split of the increase into value and rate, and the change in what to set aside each month.
Formula
Assessed value this year = the value on the new notice, but no more than last year's assessed value × (1 + cap) when a cap applies. Taxable value = assessed value − exemptions, never below zero. Bill = taxable value × mill rate ÷ 1,000, for last year and for this year, and the increase is the difference. The split takes the value change first, at last year's rate: from value = (this year's taxable value − last year's) × last year's rate ÷ 1,000; from rate = this year's taxable value × (this year's rate − last year's rate) ÷ 1,000. The two add up exactly to the increase. Value the cap kept off the roll = notice value − capped value; its saving = (taxable value without the cap − taxable value with it) × this year's rate ÷ 1,000. Rate that would have held the bill flat = last year's bill ÷ this year's taxable value × 1,000. Monthly set-aside = bill ÷ 12.
Example
Last year a home was assessed at $300,000 and taxed at 18.50 mills after a $50,000 homestead exemption: $250,000 of taxable value and a $4,625.00 bill. This year's notice values it at $345,000, 15% more, but a 2.7% assessment cap holds the assessment to $308,100, keeping $36,900 off the roll. After the exemption the taxable value is $258,100, and at 18.90 mills the bill is $4,878.09, up $253.09 or 5.5%. The higher value accounts for $149.85 of the increase and the higher rate for $103.24. Without the cap the bill would have been $5,575.50. The monthly set-aside rises $21.09, from $385.42 to $406.51, and a rate of 17.919 mills would have kept the bill at last year's amount.
Definitions
- Assessed value
- The value the assessor places on a property for tax purposes. It can be below market value where a cap or an assessment ratio applies.
- Taxable value
- Assessed value less exemptions. It is the figure the tax rate is applied to.
- Assessment cap
- A limit on how much a property's assessed value can rise in a year, such as California's 2% under Prop 13 or Florida's Save Our Homes limit of the lower of 3% or the CPI change.
- Mill rate
- A tax rate in dollars per $1,000 of taxable value. Ten mills equal 1%. A bill usually combines the mill rates of several taxing bodies.
- Homestead exemption
- An amount taken off the assessed value of a primary residence before tax is figured. Florida's can reduce taxable value by as much as $50,000.
Good to know
How a property tax bill is built
Every real estate tax bill follows the same basic arithmetic, even though the names differ from state to state. It starts with a value the assessor assigns to the property. In some places that is close to market value; in others it is a fixed percentage of market value, or a value held down by an assessment cap. Exemptions come off next. A homestead exemption for a primary residence is the most common, and there are often others for older owners, veterans or people with disabilities. What remains is the taxable value. The tax rate is then applied to the taxable value. Rates are quoted three ways: as a percentage, as dollars per $100 of value, or in mills, dollars per $1,000. This page uses mills because many bills and notices do, and the conversion is simple: 1% is 10 mills, and $1 per $100 is also 10 mills. The rate on a bill is usually the sum of several rates, one for each taxing body: the county, the city or town, the school district and special districts for things such as fire protection, libraries or water management. In the example, a home was assessed at $300,000 last year, a $50,000 homestead exemption brought the taxable value to $250,000, and a combined rate of 18.50 mills produced a bill of $4,625.00. This year the assessment is $308,100 after a cap, the taxable value $258,100, the rate 18.90 mills and the bill $4,878.09. Knowing how the bill is built tells you where to look when it rises. The value is set by the assessor, and most places give owners a window to appeal it. The exemptions depend on applications you may or may not have filed. The rates are set in public budget hearings by each taxing body. Each part has a different remedy.
Assessment caps: Prop 13, Save Our Homes and the gap they create
Several states limit how fast the assessed value of a home can rise, so that a surge in market prices does not arrive on the tax bill all at once. The two best-known limits are in California and Florida. California's Prop 13, now part of the state constitution, sets a property's value when it is purchased, newly built or changes ownership, and lets that value rise with inflation by no more than 2% a year. It also allows the value to be reduced when the property loses value. Florida's Save Our Homes limit, in section 193.155 of the Florida Statutes, caps the yearly increase in a homestead's assessed value at the lower of 3% or the change in the consumer price index for the previous calendar year. The Florida Department of Revenue's table shows how that has played out: the cap was 3.0% for 2022, 2023 and 2024, when the index change was 7.0%, 6.5% and 3.4%, then 2.9% for 2025 and 2.7% for 2026. In the example, the notice values the home at $345,000, 15% above last year's assessment of $300,000, but a 2.7% cap holds the assessment to $308,100. That keeps $36,900 of value off the tax roll and saves $697.41 this year; without the cap the bill would be $5,575.50 rather than $4,878.09. Caps create a gap between market value and assessed value that widens every year prices outrun the cap. The gap is valuable, and it is tied to the home and the owner. In California the value resets when the property changes hands. In Florida the exemption cannot be transferred, but an owner who moves may be able to carry, or port, all or part of the difference to a new Florida homestead. Anyone comparing the tax on a home they might buy with the tax the seller pays should expect the cap to restart at a much higher value.
Separating a reassessment from a rate change
When a bill rises, it helps to know how much comes from a higher value and how much from a higher rate, because they call for different responses. The page splits the increase in one stated order. It first prices the change in taxable value at last year's rate, then prices the change in rate on this year's taxable value. In the example, the $253.09 increase breaks into $149.85 from the value, $8,100 more taxable value at 18.50 mills, and $103.24 from the rate, 0.40 mills more on $258,100. The two parts always add up exactly to the increase. If the order were reversed, pricing the rate change first on last year's value, the parts would shift slightly, but the total would not change, which is why the order is stated. A second number helps judge the rate side: the rate that would have produced last year's bill from this year's taxable value. In the example it is 17.919 mills. Had the taxing bodies adopted that rate, the higher value would have been fully offset and the bill would not have changed. They adopted 18.90 mills instead, so the rate rose when it would have had to fall. That comparison is useful at budget hearings, where local governments sometimes describe an unchanged rate as holding taxes flat even though rising values raise the bill. The value side has its own remedy. If you believe the assessor has overvalued the home, most jurisdictions allow an informal review and a formal appeal within a set period after the notice is mailed, and evidence such as recent sales of comparable homes carries the most weight. With a cap in place, an appeal matters less in a rising market, because the cap rather than the market value sets the assessment. With no cap, every dollar of value that is overstated is taxed at the full rate.
What a higher bill does to an escrowed mortgage payment
Most homeowners with a mortgage do not pay the property tax bill directly. The mortgage servicer collects a share with each monthly payment, holds it in an escrow account and pays the bill when it is due. A higher bill therefore reaches the household as a higher mortgage payment, and the change can be larger than it looks. The basic change is the tax increase divided by 12. In the example the monthly set-aside rises from $385.42 to $406.51, $21.09 a month. That is the long-run effect. The first year can be higher. Servicers review escrow accounts once a year, and if the account paid a bill larger than the amount collected, because the old monthly figure was in place when the new bill arrived, the analysis finds a shortage. The servicer usually spreads that shortage over the following year's payments, on top of the new monthly amount, and may also keep a cushion in the account. The escrow account page works through the shortage, the cushion and the resulting payment, and it takes insurance changes into account too. A few practical steps help. Watch for the assessment notice and the proposed rates, which usually arrive months before the bill, and set aside the difference early rather than waiting for the escrow analysis. Check that exemptions you are entitled to have been applied, since a missing homestead exemption can cost more than any rate change. Remember that property tax is deductible on a federal return only if you itemize, and only within the cap on state and local tax deductions; the itemized deductions page decides whether itemizing is worth it. Finally, a rising assessment usually signals a rising home value, which is good news on paper; the home value against inflation page asks whether the house has actually kept ahead once taxes and upkeep are counted.
Frequently asked questions
Why did my property tax go up?
Because the taxable value rose, the combined tax rate rose, or both. In the example the bill rises from $4,625.00 to $4,878.09, which is $253.09 or 5.5%. Of that, $149.85 comes from a higher taxable value at last year's rate of 18.50 mills and $103.24 from the rate rising to 18.90 mills.
How does an assessment cap work?
It limits how much the assessed value of a home can rise in a year, whatever happens to its market value. In the example the notice shows $345,000, 15% more than last year's $300,000, but a 2.7% cap holds the assessment to $308,100. That keeps $36,900 of value off the tax roll and saves $697.41 this year. Without the cap the bill would be $5,575.50, an increase of $950.50.
What is the Save Our Homes cap for 2026?
2.7%. Under Florida law the assessed value of a homestead can rise each year by no more than the lower of 3% or the change in the consumer price index for the previous year, and the Florida Department of Revenue lists 2.7% for 2026. An owner who moves may be able to carry, or port, part of the difference between market value and assessed value to a new Florida homestead.
How does Prop 13 limit property taxes in California?
The California Constitution sets a property's value when it is purchased, newly built or changes ownership, and lets that value rise with inflation by no more than 2% a year. The value can also be reduced when the property loses value. Enter 2 in the cap field for a California home that has not changed hands since last year's assessment.
What is a mill rate?
A mill is one-thousandth of a dollar, so a rate of 18.90 mills is $18.90 of tax for every $1,000 of taxable value. That is the same as 1.890% of taxable value or $1.890 per $100. Multiply a percentage rate or a rate per $100 by 10 to get mills.
How much will my mortgage payment go up?
If your servicer pays the tax from escrow, by at least the tax increase divided by 12: $21.09 a month in the example, taking the monthly set-aside from $385.42 to $406.51. The first year can be higher, because the servicer's escrow analysis may also collect a shortage from the months paid at the old amount. The escrow account page works that out.
What tax rate would have kept my bill the same?
Last year's bill divided by this year's taxable value, times 1,000. In the example it is 17.919 mills. The combined rate went to 18.90 mills instead, 0.981 mills above it, so the rate rose when it would have had to fall to offset the higher value.