Distance between cities › USA › South Dakota › Armour, SD › Distance from Armour to Grass Range Book Hotels

Distance from Armour, SD to Grass Range, MT

Distance

688 mi

Time

12 hours 22 mins

Gas Cost

$64 - $125

There are 569.56 miles from Armour to Grass Range in northwest direction and 688 miles (1,107.23 kilometers) by car, following the I-90 route.

Armour and Grass Range are 12 hours 22 mins far apart, if you drive non-stop .

This is the fastest route from Armour, SD to Grass Range, MT.

Please note the time difference between Armour, SD and Grass Range, MT is 1 hour. The current time in Armour is 8:57 am and the current time in Grass Range is 7:57 am.

Any questions or tips to share?

Share with fellow travellers any question or tips about the route from Armour, SD to Grass Range, MT:

Lowest Price Rental Cars in Armour, SD

Planning on renting a car to go from Armour, SD to Grass Range, MT? Here there are some offers to rent a car in Armour, SD

Small

From $14

Intermediate

From $18

Full-size

From $24

SUVs

From $28

Vans

From $40

Compare rental car prices in Armour »

Gas Consumption and Emissions

A car with a fuel efficiency of MPG will need 27.61 gallons of gas to cover the route between Armour, SD and Grass Range, MT.

The estimated cost of gas to go from Armour to Grass Range is $90.07.

During the route, an average car will release 540.98 pounds of CO₂ to the atmosphere. The carbon footprint would be 0.79 pounds of CO₂ per mile.

Average USA gas price used for calculation is $3.26 per gallon of regular gas. Price last updated on March 12, 2026.
Read more about our CO₂ calculation.

Halfway Point Between Armour, SD and Grass Range, MT

If you want to meet halfway between Armour, SD and Grass Range, MT or just make a stop in the middle of your trip, the exact coordinates of the halfway point of this route are 44.718799 and -103.913997, or 44º 43' 7.6764" N, 103º 54' 50.3892" W. This location is 343.77 miles away from Armour, SD and Grass Range, MT and it would take approximately 6 hours 11 mins to reach the halfway point from both locations.

Closest City or Town to Halfway Point

The closest town to the halfway point is Belle Fourche, SD, situated 335 miles from Armour, SD and 353 miles from Grass Range, MT. It would take 5 hours 39 mins to go from Armour to Belle Fourche and 6 hours 42 mins to go from Grass Range to Belle Fourche.