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

Distance from Armour, SD to Roundup, MT

Distance

643 mi

Time

11 hours 19 mins

Gas Cost

$60 - $117

There are 543.35 miles from Armour to Roundup in northwest direction and 643 miles (1,034.81 kilometers) by car, following the I-90 route.

Armour and Roundup are 11 hours 19 mins far apart, if you drive non-stop .

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

Please note the time difference between Armour, SD and Roundup, MT is 1 hour. The current time in Armour is 10:02 am and the current time in Roundup is 9:02 am.

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Lowest Price Rental Cars in Armour, SD

Planning on renting a car to go from Armour, SD to Roundup, 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 25.84 gallons of gas to cover the route between Armour, SD and Roundup, MT.

The estimated cost of gas to go from Armour to Roundup is $84.29.

During the route, an average car will release 506.24 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 Roundup, MT

If you want to meet halfway between Armour, SD and Roundup, MT or just make a stop in the middle of your trip, the exact coordinates of the halfway point of this route are 44.510382 and -103.680408, or 44º 30' 37.3752" N, 103º 40' 49.4688" W. This location is 321.70 miles away from Armour, SD and Roundup, MT and it would take approximately 5 hours 39 mins to reach the halfway point from both locations.

Closest City or Town to Halfway Point

The closest town to the halfway point is Saint Onge, SD, situated 323 miles from Armour, SD and 321 miles from Roundup, MT. It would take 5 hours 23 mins to go from Armour to Saint Onge and 5 hours 56 mins to go from Roundup to Saint Onge.