Quick answer: Most money questions come down to a few formulas: percentage change is (new − old) ÷ old × 100, the price before sales tax is total ÷ (1 + rate), and a mortgage payment uses the amortization formula. The tools below apply them, and the state tools add current tax rates and fees for vehicles, income and property.

Which tool do you need?

Question	Use
What is 15% of 240, or how much did a price change?	Percentage Calculator
What did an item cost before tax?	Reverse Sales Tax Calculator
What will my monthly mortgage payment be?	Mortgage Calculator
How much tax and fees will I pay on a car?	Vehicle Tax Calculator, or the Texas and Oklahoma tools
How much New York State income tax will I owe?	NY State Tax Calculator
What is my Michigan property tax bill?	Michigan Property Tax Calculator

Money formulas in one place

Calculation	Formula	Example
Percent of a number	X ÷ 100 × Y	15% of 240 = 36
Percentage change	(new − old) ÷ old × 100	80 to 100 = 25%
Price before sales tax	total ÷ (1 + rate)	$108.25 ÷ 1.0825 = $100
Sales tax with a trade-in	(price − trade-in) × rate	($35,000 − $10,000) × 6.25% = $1,562.50
Monthly mortgage payment	P × r(1+r)^n ÷ ((1+r)^n − 1)	$300,000, 6.5%, 30 years = $1,896.20
Property tax from millage	taxable value × mills ÷ 1,000	$150,000 × 40 mills = $6,000

Tax facts to check before you calculate

Sales tax rates stack. Use the combined state and local rate shown on the receipt.
Trade-ins lower car tax in most states, but not in California, Hawaii, Virginia or Washington, DC.
Percentage points and percent differ. A rate going from 4% to 5% is up 1 point, or 25%.
Mortgage payments exclude taxes and insurance unless the tool adds PITI.
State tools use published rates and link to the official source on each page.

Glossary

Term	Meaning
Combined sales tax rate	State plus county, city and district rates.
Trade-in credit	Reducing the taxable price of a vehicle by the value of the vehicle you trade.
Amortization	Repaying a loan in equal payments that shift from interest to principal over time.
PITI	Principal, interest, taxes and insurance.
Millage	Property tax rate in mills: $1 per $1,000 of taxable value.
Excise tax	A tax on a specific item, such as Oklahoma’s vehicle excise tax.

Guides that explain the maths

Percentage increase and decrease

The change formula with examples

How to calculate sales tax backwards

Pre-tax price from a total

Car sales tax and trade-in credits

Every state, 2026

How mortgage payments are calculated

Formula and amortization

Frequently asked questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. 15% of 240 is 0.15 × 240 = 36.

How do I take sales tax out of a total?

Divide the total by 1 plus the tax rate. $107 at 7% is $100 before tax.

How is a mortgage payment calculated?

With the amortization formula M = P × r(1+r)^n ÷ ((1+r)^n − 1). Taxes, insurance and PMI are added on top.

Does a trade-in reduce car sales tax?

In most states, yes. You pay tax on the price minus the trade-in. A few states give no credit or cap it.

Are the tax calculators up to date?

Each state tool shows the rates it uses and links to the official source. Rates are reviewed when states publish changes.

Are these calculators free?

Yes, every tool is free with no account needed.

Tax and loan tools give estimates for planning. Confirm final figures with your lender, state revenue department or DMV. This is not financial or tax advice.

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Written and checked by Amara Taylor

Content Lead, Anchor AI Tools, California, USA. Spotted an error? Email hello@anchoraitools.com and it will be checked and corrected. See our editorial standards.

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