The map above shows Idaho and Montana side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Idaho vs Montana Geography
Land area: Idaho has a land area of 82,645 square miles (214,051 km²), while Montana has 145,550 square miles (376,973 km²). Montana's land area is 1.8 times (76%) larger than Idaho's.
Total area: Idaho: 83,569 square miles (216,441 km²) vs Montana: 147,043 square miles (380,840 km²), including inland and coastal water. Montana's total area is 1.8 times (76%) larger than Idaho's.
Length: Idaho is 483 miles (778 km) long from north to south; Montana is 319 miles (514 km). Idaho's north-south length is 1.5 times (51%) longer than Montana's.
Width: Idaho spans 352 miles (566 km) east to west; Montana spans 607 miles (976 km). Montana's east-west width is 1.7 times (72%) wider than Idaho's.
Highest point: Idaho's highest point is Borah Peak at 12,631 feet (3,850 m); Montana's is Granite Peak at 12,767 feet (3,891 m). Granite Peak is 136 feet higher than Borah Peak.
Lowest point: Idaho's lowest point is Snake River at 718 feet; Montana's is Kootenai River at 1,805 feet. Idaho's lowest point is 1,087 feet lower.
Idaho vs Montana Population and History
Population: Idaho has a population of 2,001,619 (2024), while Montana has 1,137,233 (2024). Idaho's population is 1.8 times (76%) larger than Montana's.
Population density: Idaho: 24.2 people per square mile vs Montana: 7.8. Idaho's population density is 3.1 times (210%) higher than Montana's.
Biggest city: Idaho's biggest city is Boise with 237,963 people; Montana's is Billings with 121,483. Boise's population is 2.0 times (96%) larger than Billings'.
Largest metro area: Idaho's largest metropolitan area is Boise City, ID metro area (845,877 people) vs Montana's Billings, MT metro area (192,531). Boise City, ID metro area's population is 4.4 times (339%) larger than Billings, MT metro area's.
History: Idaho: Admitted to the Union on July 3, 1890, as the 43rd state. Montana: Admitted to the Union on November 8, 1889, as the 41st state. In its current form, Montana is the older of the two by 1 years.
Idaho vs Montana Economy
GDP: Idaho's GDP is $129.0 billion (2024) vs Montana's $78.4 billion. Idaho's economic output is 1.6 times (65%) larger than Montana's.
GDP per capita: Idaho: $64,457 per person vs Montana: $68,975. Montana's GDP per capita is 1.1 times (7%) higher than Idaho's.
Average income: Idaho: $62,323 vs Montana: $69,240 average income per person (per capita personal income). Montana's average income is 1.1 times (11%) higher than Idaho's.
Idaho vs Montana Counties
Number of counties: Idaho has 44 counties, while Montana has 56. Montana's county count is 1.3 times (27%) higher than Idaho's.
Biggest county by area: Idaho's largest county is Idaho County at 8,478 square miles; Montana's is Beaverhead County at 5,543 square miles. Idaho County's land area is 1.5 times (53%) larger than Beaverhead County's.
Smallest county by area: Idaho: Payette County (407 sq mi) vs Montana: Silver Bow County (718 sq mi). Silver Bow County's land area is 1.8 times (76%) larger than Payette County's.
Most populous county: Idaho: Ada County (535,799 people) vs Montana: Yellowstone County (171,583 people). Ada County's population is 3.1 times (212%) larger than Yellowstone County's.
Least populous county: Idaho: Clark County (794 people) vs Montana: Petroleum County (525 people). Clark County's population is 1.5 times (51%) larger than Petroleum County's.
Richest county: Idaho: Blaine County ($202,612 per capita income) vs Montana: Gallatin County ($94,573). Blaine County's income is 2.1 times (114%) richer than Gallatin County's.
Poorest county: Idaho: Madison County ($29,485 per capita income) vs Montana: Blaine County ($37,554). Blaine County's income is 1.3 times (27%) richer than Madison County's.
Idaho vs Montana Taxes
State income tax: Idaho has a top income tax rate of 5.3%, while Montana has a top income tax rate of 5.65%. Montana's top rate is 0.35 percentage points higher.
Property tax: Idaho: 0.43% effective rate vs Montana: 0.69% of home value per year. Montana's rate is 0.26 percentage points higher.
Sales tax: Idaho: 6.03% combined state and average local rate vs Montana: 0%. Idaho's combined rate is 6.03 percentage points higher.
Official Websites
Idaho official website · Montana official website
More Size Comparisons
All Idaho size comparisons · All Montana size comparisons
Area, elevation and boundary figures come from official national statistics and US Census Bureau and Natural Earth boundary data; US state population, economic, county and tax figures come from the US Census Bureau, the Bureau of Economic Analysis and the Tax Foundation. Figures are rounded and for general reference.