How far is Byrnes Mill, MO from O'Fallon, MO?
The driving distance from Byrnes Mill, MO to O'Fallon, MO is about 44.2 miles (71.2 km), with a travel time of about 00h 51m by car.
- The straight-line flight distance is about 26.5 miles (42.7 km).
- For a round trip, plan for roughly 01h 43m 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 00h 51m.
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.
Township in Missouri, United States
Route Weather Snapshot
Check the forecast at both ends before you head out.
Showers And Thunderstorms Likely
Slight Chance Showers And Thunderstorms
Driving Route Map
The map below follows the saved road route between Byrnes Mill and O'Fallon.
Turn-by-Turn Driving Directions
Step-by-step road directions between Byrnes Mill and O'Fallon.
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1
Start on Upper Byrnes Mill Road
1.4 mi · 3 min · Upper Byrnes Mill Road
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2
Merge right
1695 ft · 24 sec
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3
Take the exit left toward MO 30 East
36 m · 2 sec
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4
Merge slight right
5.9 mi · 8 min
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5
Take the exit slight left toward New Sugar Creek Road
148 m · 13 sec
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6
Turn slight left onto New Sugar Creek Road
1.1 mi · 2 min · New Sugar Creek Road
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7
Continue on Hawkins Road
1.6 mi · 4 min · Hawkins Road
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8
Turn left
8.8 mi · 14 min
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9
Take the exit slight left toward I 64 West, US 40 West, US 61 North: Wentzville
41 m · 7 sec
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10
Turn left onto I 64 West, US 40 West, US 61 North: Wentzville
1812 ft · 44 sec
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11
Merge slight left onto Avenue of the Saints
11.7 mi · 15 min · Avenue of the Saints
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12
Take the exit slight right toward MO K: O'Fallon
100 m · 6 sec
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13
Merge slight right onto North Outer Road
1650 ft · 31 sec · North Outer Road
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14
Continue on North Outer Road
946 ft · 18 sec · North Outer Road
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15
Turn right
3.3 mi · 5 min
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16
Continue straight
1.5 mi · 3 min
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17
Continue straight
1.6 mi · 3 min
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18
Continue on South Main Street
3115 ft · 2 min · South Main Street
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19
Turn right
8 m · 2 sec
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20
Arrive at your destination
0 m · 1 sec
Car Route Details
A richer read on the saved driving route between Byrnes Mill and O'Fallon.
Turn-heavy local drive
The route has frequent decision points for its length, so lane choice and turn timing will matter more than cruising speed.
Avenue of the Saints
Merge slight left onto Avenue of the Saints
11.7 mi · 00h 15m
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.
Showers And Thunderstorms Likely leaving Byrnes Mill and Slight Chance Showers And Thunderstorms near O'Fallon.
Trip Questions
Direct answers travelers usually want before committing to the drive.
How long does it take to drive from Byrnes Mill to O'Fallon?
The road trip is about 44.2 miles (71.2 km) and usually takes 00h 51m 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?
Lake is a useful midpoint, sitting about 19.3 miles from Byrnes Mill and 24.9 miles from O'Fallon.
How much longer is the road route than the straight-line distance?
The direct path is about 26.5 miles (42.7 km), while the road route adds roughly 17.7 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 4:46 PM CDT.
How much will gas cost for this route?
Using about 28.3 MPG, regular gas is estimated at $5.88 one way or $11.77 round trip. Estimated CO2 is about 13.9 kg one way.
What should you check before leaving?
Before you leave, expect Showers And Thunderstorms Likely around Byrnes Mill and Slight Chance Showers And Thunderstorms near O'Fallon.
Stop Ideas Near Lake
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 Lake.
Kirkwood
Gateway Transportation Center
Alton
Washington
Flight Path Map
This map shows the direct air route between Byrnes Mill and O'Fallon. Straight-line distance: 26.53 mi (42.7 km).
#1 Byrnes Mill
City in Jefferson County, Missouri, United States
| Population | 3,015 |
| Coordinates | 38.4378300, -90.5817900 |
| Altitude | 143 |
| Country | United States |
#2 O'Fallon
The most populous city in St.
| Population | 89,769 |
| Coordinates | 38.8106100, -90.6998500 |
| Altitude | 165 |
| Country | United States |
End: (-90.699849, 38.810674)
Estimated Travel Time
Distance: 71 km by road
| Speed | Time |
|---|---|
| 30 mph (48.3 km/h) | 01h 28m |
| 40 mph (64.37 km/h) | 01h 06m |
| 50 mph (80.47 km/h) | 00h 53m |
| 60 mph (96.56 km/h) | 00h 44m |
| 70 mph (112.65 km/h) | 00h 37m |
| 80 mph (129 km/h) | 00h 33m |
Fuel, Round Trip and CO2
Estimated fuel cost and emissions for this route.
| Fuel | $/gal | One way | Round trip |
|---|---|---|---|
| Regular gas | $3.77 | $5.88 | $11.77 |
| Mid-grade | $4.25 | $6.63 | $13.27 |
| Premium | $4.65 | $7.26 | $14.52 |
| Diesel | $5.30 | $8.27 | $16.55 |
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 · May 26, 2026
Distance to Other Cities
Planning a road trip? See the full trip guide on Trip.ovh — stops, fuel costs, weather, and departure timing.