How far is O'Fallon, MO from Flat River, MO?
The driving distance from O'Fallon, MO to Flat River, MO is about 87.4 miles (140.6 km), with a travel time of about 01h 46m by car.
- The straight-line flight distance is about 67.1 miles (108 km).
- For a round trip, plan for roughly 03h 33m of driving time before adding stops, traffic, or weather delays.
- A comfortable departure window is usually 8:00 AM to 10:00 AM CDT.
Reverse, save, or send this route
This route works well as a day trip with time at the destination. Copy the route link, send it to another device, or print a clean version before you head out.
This route works well as a day trip with time at the destination.
Flight Distance
Driving Distance
Gas Cost Calculator
Leave and Arrive Planner
Pick a departure time to see your estimated arrival and same-day return window.
Drive time stays fixed at 01h 46m.
A morning start gives you useful time at the destination and keeps the return out of the late evening.
You are leaving earlier than the recommended window, which gives you extra margin for breaks and traffic.
Halfway Point
A useful midpoint for breaks, coffee, or meeting in the middle.
City in Jefferson County, Missouri, United States
Route Weather Snapshot
Check the forecast at both ends before you head out.
Mostly Sunny
Sunny
Driving Route Map
The map below follows the saved road route between O'Fallon and Flat River.
Turn-by-Turn Driving Directions
Step-by-step road directions between O'Fallon and Flat River.
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1
Start on the route
8 m · 7 sec
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2
Turn left onto South Main Street
3116 ft · 2 min · South Main Street
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3
Turn left onto Drennen Parkway
1.4 km · 1 min · Drennen Parkway
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4
Take the ramp slight left toward I 70 East: Saint Louis
133 m · 6 sec
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5
Merge slight left
13.5 mi · 17 min
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6
Take the exit slight right toward I 270: Chicago, Memphis
872 ft · 12 sec
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7
Keep slight right to continue on I 270 South: Memphis
2339 ft · 33 sec
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8
Continue on I 270 South: Memphis
723 ft · 10 sec
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9
Merge slight left
19 mi · 24 min
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10
Take the exit slight right toward I 55, US 61, US 67: Saint Louis, Memphis, Lemay Ferry Road
1911 ft · 27 sec
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11
Keep slight right to continue on I 55 South: Memphis
2031 ft · 44 sec
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12
Merge slight left onto Rosa Parks Highway
1.5 mi · 2 min · Rosa Parks Highway
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13
Continue on Officer Thomas G. Smith, Jr. Memorial Highway
1.8 mi · 2 min · Officer Thomas G. Smith, Jr. Memorial Highway
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14
Continue on Police Officer Steven Jarvis Memorial Highway
18.3 mi · 20 min · Police Officer Steven Jarvis Memorial Highway
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15
Take the exit slight right toward US 67 South: Farmington, Poplar Bluff
914 ft · 20 sec
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16
Keep slight left
729 ft · 18 sec
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17
Enter the roundabout and take exit 1 toward the route
9 m · 1 sec
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18
Exit the roundabout
26.4 mi · 30 min
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19
Take the exit slight right toward US 67 Business, MO 8: Desloge, Park Hills
836 ft · 22 sec
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20
Turn right
107 m · 7 sec
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21
Turn left onto North Desloge Drive
1.9 mi · 3 min · North Desloge Drive
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22
Continue on Taylor Avenue
1.4 km · 2 min · Taylor Avenue
-
23
Continue on Coffman Street
116 m · 14 sec · Coffman Street
-
24
Turn left onto West Main Street
1420 ft · 32 sec · West Main Street
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25
Turn left onto Crane Street
93 m · 8 sec · Crane Street
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26
Arrive at your destination
0 m · 1 sec · Crane Street
Car Route Details
A richer read on the saved driving route between O'Fallon and Flat River.
Highway-focused drive
Most of the mileage stays on named highways, so the important moments are ramps, exits, merges, and the final local approach.
US 67 South
Exit the roundabout
26.4 mi · 00h 30m
Route Summary
A quick read on whether this route feels easy, ambitious, or worth planning around.
A comfortable day-trip route
This route works well as a day trip. You can leave in the morning, spend meaningful time at the destination, and still return the same day.
Mostly Sunny leaving O'Fallon and Sunny near Flat River.
Trip Questions
Direct answers travelers usually want before committing to the drive.
How long does it take to drive from O'Fallon to Flat River?
The road trip is about 87.4 miles (140.6 km) and usually takes 01h 46m in normal driving conditions.
Is this a same-day trip or an overnight route?
This route works well as a day trip. You can leave in the morning, spend meaningful time at the destination, and still return the same day.
What is the halfway point on this route?
Kimmswick is a useful midpoint, sitting about 43.7 miles from O'Fallon and 43.7 miles from Flat River.
How much longer is the road route than the straight-line distance?
The direct path is about 67.1 miles (108 km), while the road route adds roughly 20.3 extra miles because roads do not follow the straight air line.
When is the best time to leave for this route?
A good departure window is usually 8:00 AM to 10:00 AM CDT. If you want a more comfortable same-day return, try to leave by 2:56 PM CDT.
How much will gas cost for this route?
Using about 28.3 MPG, regular gas is estimated at $11.61 one way or $23.23 round trip. Estimated CO2 is about 27.4 kg one way.
What should you check before leaving?
Before you leave, expect Mostly Sunny around O'Fallon and Sunny near Flat River.
Stop Ideas Near Kimmswick
Useful break, food, and waypoint ideas within about 15 miles of the route midpoint.
Transit and Meeting Points
Useful pickup, handoff, or rendezvous points close to Kimmswick.
Kirkwood
Gateway Transportation Center
Washington
Alton
Flight Path Map
This map shows the direct air route between O'Fallon and Flat River. Straight-line distance: 67.11 mi (108 km).
#1 O'Fallon
The most populous city in St.
| Population | 89,769 |
| Coordinates | 38.8106100, -90.6998500 |
| Altitude | 165 |
| Country | United States |
#2 Flat River
River in Michigan, United States of America
| Population | 5,157 |
| Coordinates | 37.8500500, -90.5167900 |
| Altitude | 219 |
| Country | United States |
End: Flat River (-90.51679, 37.85005)
Estimated Travel Time
Distance: 141 km by road
| Speed | Time |
|---|---|
| 30 mph (48.3 km/h) | 02h 54m |
| 40 mph (64.37 km/h) | 02h 11m |
| 50 mph (80.47 km/h) | 01h 44m |
| 60 mph (96.56 km/h) | 01h 27m |
| 70 mph (112.65 km/h) | 01h 14m |
| 80 mph (129 km/h) | 01h 05m |
Fuel, Round Trip and CO2
Estimated fuel cost and emissions for this route.
| Fuel | $/gal | One way | Round trip |
|---|---|---|---|
| Regular gas | $3.77 | $11.61 | $23.23 |
| Mid-grade | $4.25 | $13.10 | $26.20 |
| Premium | $4.65 | $14.33 | $28.67 |
| Diesel | $5.30 | $16.34 | $32.67 |
Assumes 8.3 L/100 km (about 28.3 MPG). CO2 is an estimate and varies by vehicle, fuel blend, traffic, and terrain.
Prices in Missouri · Apr 23, 2026
Distance to Other Cities
Planning a road trip? See the full trip guide on Trip.ovh — stops, fuel costs, weather, and departure timing.