Illinois vs Montana
A tax calculator says the difference is $5,068 a year. Once you count what a dollar actually buys in each, Montana is $9,181 ahead — $91,809 over 10 years.
Property tax is set by counties, not states. Inside Texas alone the rate varies six times over, so this is the single choice that changes the answer most.
Does it work everywhere in Montana?
in what the money buys · $91,809 over 10 years
A pay cut of up to $13,424 (13.4%) still leaves you level.
Who worked this out, and what it is built on
I build and maintain every comparison on this site — 1275 state pairs so far, on the same engine that runs the tax calculators for all 50 states and 3,143 counties. This is not a template with two names swapped into it: Illinois and Montana are run through the actual rules of each place, and if the numbers say the move is not worth it, that is what the page says.
Four sources, and one deliberate refusal. Federal figures from the IRS revenue procedure. State rates read one state at a time off each state’s own department of revenue. County property tax from the US Census Bureau. Cost of living from the Bureau of Economic Analysis Regional Price Parities, 2024 — and not from Numbeo or any other crowd-sourced index, because those are filled in by users, publish no methodology, and cannot be cited. That single choice is most of why the cost-of-living numbers here differ from everybody else’s.
When I get something wrong I publish the correction with the date and what it cost — including the two mistakes on these pages I found myself. Data last verified September 1, 2026.
Where to go from here
Almost nobody is choosing between exactly two places. These are the questions that usually come next, with the answer already attached so you can see which is worth opening.
Other moves involving Illinois or Montana
States that sit near Montana on prices compared against Illinois, and the mirror of that. The comparison you would run next.
- Illinois vs North Carolina— North Carolina by $10,374
- Illinois vs Wisconsin— Wisconsin by $6,848
- Illinois vs South Carolina— South Carolina by $11,198
- Montana vs Nevada— Nevada by $979
- Delaware vs Montana— Montana by $3,936
- Arizona vs Montana— Montana by $1,667
Each state on its own
The full detail behind each half of the comparison above.
The counties that decide it
Property tax is set by county, and the spread inside one state beats most state pairs.
- Pulaski County, Illinois— 0.82%, the cheapest
- Lake County, Illinois— 2.68%, the dearest
- Madison County, Montana— 0.41%, the cheapest
- Blaine County, Montana— 1.52%, the dearest
Similar in price to Illinois
States that sit next to Illinois on the price index — often the comparison people should have run.
- Rhode Island— 102.3 on prices
- Virginia— 101.1 on prices
- Arizona— 100.7 on prices
- Nevada— 100 on prices
- Every Illinois comparison— all 50
- Every Montana comparison— all 50
- The nine states with no income tax— and what they charge instead
Montana leaves you $9,181 a year better off — not the number you were expecting
On $100,000 with a $400,000 home, the take-home difference between Illinois and Montana is $5,068 a year. That is what a tax calculator gives you, and it is a nominal figure: it treats a dollar in Illinois and a dollar in Montana as the same thing.
They are not. On the Bureau of Economic Analysis price index Illinois is 100 and Montana is 94.6, where 100 is the national average. Deflate each take-home by where it gets spent and what the money actually buys is $66,989 in Illinois against $76,170 in Montana — a real difference of $9,181 a year, 1.8× the nominal one, and $91,809 over the 10 years most people stay.
Where the two sit nationally: Illinois is the 18th most expensive place to live of the 51 — the 50 states and the District of Columbia — and Montana is 30th. Housing, the component that moves most, is 93.9 against 84.6.
Grey columns are what a year of Illinois and a year of Montana are worth in the same money. The bars between them are each thing that changes, in the order it changes: green adds, amber takes away.
Where the money actually goes, line by line
Five separate taxes, and on this pair property tax is the biggest single difference — $4,552 against $516 for the income tax everybody quotes:
Federal income tax — $13,170 either way. Identical, because it is federal. Any comparison that shows a difference here is wrong.
FICA — $7,650 either way. Also federal, also identical.
State income tax — $4,805 in Illinois, $4,289 in Montana. A difference of $516.
Property tax — $7,386 in Illinois, $2,834 in Montana on a $400,000 home, at each state's median local rate. This is bigger than the income tax difference, and it runs the other way — which is the whole reason the headline number disappoints.
Local income tax — zero on both sides. Both Illinois and Montana keep income tax at the state level only, so the figures above are complete rather than approximations.
Total: $33,011 in Illinois against $27,944 in Montana — 33.0% and 27.9% of gross.
And Illinois housing costs 11.0% more
The cost of living figure on most comparison sites is one number from a crowd-sourced database. This is the Bureau of Economic Analysis Regional Price Parity — an official index published for every state, where 100 is the national average — and it comes split into components, which is the half that decides moves.
Cheaper in Montana than IllinoisDearer in Montana than Illinois
Each bar is how far apart Illinois and Montana are on that component, and which way. Housing almost always runs several times wider than everything else — which is why a single blended index tells you very little.
All items — 100 in Illinois, 94.6 in Montana. A gap of 5.4 points.
Housing — 93.9 against 84.6. A gap of 9.3 points, 1.7× the headline gap. This is what people mean when they say somewhere is expensive.
Goods — 103.8 against 96, 7.8 points apart — wide for goods: across all 1,275 state pairs the median goods gap is 2.7 points against 24.9 for housing, so on this pair the shopping basket genuinely differs and not just the rent.
Utilities — 85 against 72.3. 12.7 points apart, close enough not to change a decision.
Which half of this reaches you depends on whether you buy. Renting, the real difference between Illinois and Montana is $4,791 a year — property tax comes out of your side entirely, and what is left is the price level. Buying a $400,000 home it is $9,181. So buying widens the gap by $4,390: the more house you own, the more this comparison is worth to you.
The number to take into a salary negotiation: $86,576
This is the question people are actually asking and almost nobody answers: what would I need to earn in Montana to live exactly as well as I do on $100,000 in Illinois?
$86,576. That is 13.4% less than you earn now. You could take a pay cut of $13,424 moving to Montana and be no worse off — which is a very different conversation to have with a recruiter than "Montana has lower taxes".
The dashed line is the salary you earn now. The solid line is what matches it in Montana. If the relationship were a simple multiplier the two would be parallel — they are not, because brackets, the Social Security ceiling and a property tax that does not move with income all bend it.
The obvious shortcut fails here, and by a measurable amount. Scaling your salary by the ratio of price levels — $100,000 × 94.6/100 — gives $94,600. The answer is $86,576, so the shortcut is $8,024 too high: brackets, the Social Security ceiling and a property tax that ignores income all bend the line the shortcut assumes is straight.
The figure belongs to the two states and your income. On $40,000 the match in Montana is $31,251, 21.9% below what you earn; on $250,000 it is $228,583, 8.6% below. The relationship bends by 13.3% across that range.
"Illinois" and "Montana" are not places you can compare
Every figure above uses each state's median local property tax rate — its counties in Illinois, its counties in Montana — and that is a simplification the page should own rather than hide.
Montana has 56 counties, and the effective property tax rate runs from 0.41% in Madison County to 1.52% in Blaine County — 3.7 times. On a $400,000 home that is a spread of $4,454 a year, without leaving the state.
56 counties. Each dot is one. The spread is 3.7 times from end to end, which is why a state average is not a number you can plan with.
Illinois has 102 counties, and the effective property tax rate runs from 0.82% in Pulaski County to 2.68% in Lake County — 3.2 times. On a $400,000 home that is a spread of $7,409 a year, without leaving the state.
So the honest version of this question is not "Illinois or Montana" but which county. Picking the cheapest county in Montana against the dearest county in Illinois swings the property tax line by $9,074 a year; the reverse choice swings it $2,789 the other way. Against a headline difference of $9,181, the county is not a detail — it is most of the decision.
Neither Illinois nor Montana lets its counties levy their own income tax, so that layer is genuinely zero here rather than unmodelled — one of the 1,225 pairs out of 1,275 where it does not apply. It is the reason Illinois and Montana are easier to compare honestly than most neighbours are.
Over 10 years: $91,809
Nobody moves for one year, and almost no comparison prices the decision over the horizon on which it is actually made.
At $9,181 a year of real difference, 10 years in Montana instead of Illinois is worth $91,809 in today's purchasing power — before compounding anything you might invest it in.
The line starts below zero because moving costs about $15,000 and lands entirely in year one. It takes until year 2 for the move to pay for itself. That is the figure a per-year comparison hides.
The first slice of it is not yours, though. Reckoning $15,000 for removal, fees and selling costs — this page's assumption, not a sourced figure — at $9,181 a year it takes 1.6 years to earn back, so a stay shorter than that loses money on a move the annual figure calls a win.
At three horizons: $27,543 over three years, $91,809 over 10, $275,426 over thirty.
None of those figures contains the one variable that could overturn them: the same job rarely pays the same in Illinois and Montana. That is what the $86,576 break-even above is for — it prices an offer instead of assuming the offer is identical.
You could take a $13,424 pay cut to move to Montana and be no worse off
That is the version of this comparison worth taking into a negotiation, and it is not a figure any tax calculator produces.
Matching your $100,000 standard of living in Illinois takes $86,576 in Montana — 13.4% less than you earn now. So an offer of $86,576 is not a downgrade, and an offer above it is a raise however it looks on paper.
The reverse framing is the one recruiters use, and it is worth being able to answer: a company in Illinois offering to match your current salary is offering you less than the Montana job at $86,576. On 10 years the difference is $91,809.
Where every number here comes from
Four sources, each read off the body that publishes it:
US Bureau of Economic Analysis — Regional Price Parities by State and Metro Area, 2024 (released 19 February 2026) — read 2026-09-08. https://www.bea.gov/data/prices-inflation/regional-price-parities-state-and-metro-area
IRS — Revenue Procedure for the tax year (federal brackets, standard deduction and FICA) — read 2026-09-02. https://www.irs.gov/
Each state's own department of revenue (state income tax rates and deductions), verified one state at a time — read 2026-09-02. https://estimatetax.net/sources/
US Census Bureau, American Community Survey (county effective property tax rates) — read 2026-08-31. https://data.census.gov/
The cost of living index is the part worth checking, because it is where comparison sites usually reach for something crowd-sourced. The Regional Price Parities are produced by the Bureau of Economic Analysis, cover every state and metro area, and are published with a methodology document. The figures here are the 2024 release and are not extrapolated forward.
And what this page does not model:
— The cost of living index is the BEA's Regional Price Parity for 2024, the most recent published. It is not extrapolated to the current year, and it is a state-wide average — inside a state, a metro area and a rural county differ by more than most state pairs do.
— Moving costs, state transfer taxes on buying a home, and the cost of selling the one you have are not included. On a short stay they can outweigh every annual difference on this page.
— Sales tax is not modelled. It is inside the BEA index — that is what a price parity measures — but it is not broken out separately here.
— The comparison assumes the same salary in both places unless you change it. In practice a job in a high-cost state usually pays more, which is exactly what the break-even figure is for.
— Health insurance, childcare and car insurance vary enormously by state and are only inside the index as averages. If any of the three is a large part of your budget, it deserves its own arithmetic.
Where to go next
Questions
- Is it cheaper to live in Illinois or Montana?
- Montana, by $9,181 a year in real purchasing power on $100,000 with a $400,000 home. The take-home difference is only $5,068; the rest comes from the cost of living, where Illinois indexes at 100 and Montana at 94.6 against a national average of 100.
- How much do I need to earn in Montana to match $100,000 in Illinois?
- $86,576 — 13.4% less than you earn now, so a pay cut of up to $13,424 still leaves you level. That accounts for federal tax, FICA, state tax, property tax and the price level in each state.
- What are the taxes in Illinois vs Montana?
- On $100,000: state income tax of $4,805 in Illinois against $4,289 in Montana, and property tax of $7,386 against $2,834 on a $400,000 home at median county rates. Federal tax and FICA are identical in both — $13,170 and $7,650 — so any comparison showing a difference there is wrong.
- Does Montana really have lower property tax?
- That depends entirely on the county, which is why a state-level answer is not much use. Montana runs from 0.41% in Madison County to 1.52% in Blaine County — 3.7 times, or $4,454 a year on a $400,000 home. The median is 0.71%.
- How much is the difference over 10 years?
- $91,809 in today's purchasing power, at $9,181 a year. That excludes moving and housing transaction costs, which land in year one and can outweigh everything else on a short stay.
- Where does your cost of living data come from?
- The Bureau of Economic Analysis Regional Price Parities for 2024, an official index covering every state and metro area with a published methodology. Not a crowd-sourced database — and it comes broken into housing, goods, utilities and services, which matters because housing moves several times more than anything else.