How far is O'Fallon, IL from Decatur, IL?
The driving distance from O'Fallon, IL to Decatur, IL is about 112.4 miles (180.9 km), with a travel time of about 02h 01m by car.
- The straight-line flight distance is about 100.3 miles (161.4 km).
- For a round trip, plan for roughly 04h 03m 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 02h 01m.
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 Montgomery County, Illinois
Route Weather Snapshot
Check the forecast at both ends before you head out.
Slight Chance Showers And Thunderstorms then Mostly Sunny
Driving Route Map
The map below follows the saved road route between O'Fallon and Decatur.
Turn-by-Turn Driving Directions
Step-by-step road directions between O'Fallon and Decatur.
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1
Start on West State Street
1.5 km · 2 min · West State Street
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2
Enter the roundabout and take exit 2 toward West State Street
22 m · 3 sec · West State Street
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3
Exit the roundabout onto West State Street
998 ft · 28 sec · West State Street
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4
Turn right onto West Highway 50
2559 ft · 51 sec · West Highway 50
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5
Take the ramp slight right
2098 ft · 51 sec
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6
Merge slight left
1.8 mi · 2 min
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7
Take the exit slight right toward IL 159: Belleville, Collinsville
1536 ft · 29 sec
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8
Keep slight right to continue on Collinsville
67 m · 5 sec
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9
Turn straight onto North Illinois Street
3.8 mi · 6 min · North Illinois Street
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10
Continue on South Morrison Avenue
1.3 mi · 2 min · South Morrison Avenue
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11
Continue on Vandalia Street
2.8 mi · 5 min · Vandalia Street
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12
Take the ramp slight right toward I 55 North, I 70 East
2235 ft · 55 sec
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13
Merge slight left
3.8 mi · 4 min
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14
Keep slight left to continue on I 55 North, I 270 West: Chicago, Springfield, Kansas City
44 mi · 47 min
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15
Take the exit slight right toward IL 48, IL 127: Raymond, Taylorville, Hillsboro
1658 ft · 31 sec
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16
Keep slight right to continue on IL 48, IL 127: Raymond, Taylorville, Hillsboro
45 m · 3 sec
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17
Turn straight onto North 22nd Avenue
7.2 mi · 11 min · North 22nd Avenue
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18
Continue on Sarpy Street
12.2 mi · 21 min · Sarpy Street
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19
Continue on County Road 975 N
3056 ft · 52 sec · County Road 975 N
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20
Continue on Jaycee Drive
18.4 mi · 23 min · Jaycee Drive
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21
Continue on North Railroad Avenue
12.9 mi · 15 min · North Railroad Avenue
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22
Turn right onto West South Side Drive
1.3 km · 1 min · West South Side Drive
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23
Turn slight left
1.4 mi · 3 min
-
24
Turn left onto East Wood Street
155 m · 16 sec · East Wood Street
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25
Arrive at your destination
0 m · 1 sec · East Wood Street
Car Route Details
A richer read on the saved driving route between O'Fallon and Decatur.
Interchange-aware route
The drive includes several ramps, exits, or merges, so checking the next few maneuvers before busy interchanges is useful.
I 55 North
Keep slight left to continue on I 55 North, I 270 West: Chicago, Springfield, Kansas City
44 mi · 00h 47m
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.
Sunny leaving O'Fallon and Slight Chance Showers And Thunderstorms then Mostly Sunny near Decatur.
Trip Questions
Direct answers travelers usually want before committing to the drive.
How long does it take to drive from O'Fallon to Decatur?
The road trip is about 112.4 miles (180.9 km) and usually takes 02h 01m 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?
Zanesville is a useful midpoint, sitting about 57.1 miles from O'Fallon and 55.4 miles from Decatur.
How much longer is the road route than the straight-line distance?
The direct path is about 100.3 miles (161.4 km), while the road route adds roughly 12.1 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 2:26 PM CDT.
How much will gas cost for this route?
Using about 28.3 MPG, regular gas is estimated at $14.97 one way or $29.94 round trip. Estimated CO2 is about 35.3 kg one way.
What should you check before leaving?
Before you leave, expect Sunny around O'Fallon and Slight Chance Showers And Thunderstorms then Mostly Sunny near Decatur.
Stop Ideas Near Zanesville
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 Zanesville.
Carlinville
Springfield station
Alton
Gateway Transportation Center
Flight Path Map
This map shows the direct air route between O'Fallon and Decatur. Straight-line distance: 100.28 mi (161.39 km).
#1 O'Fallon
Township in St.
| Population | 29,606 |
| Coordinates | 38.5922700, -89.9112100 |
| Altitude | 167 |
| Country | United States |
#2 Decatur
The most populous city in Macon County, Illinois.
| Population | 70,007 |
| Coordinates | 39.8403100, -88.9548000 |
| Altitude | 205 |
| Country | United States |
End: East Wood Street (-88.954801, 39.840341)
Estimated Travel Time
Distance: 181 km by road
| Speed | Time |
|---|---|
| 30 mph (48.3 km/h) | 03h 44m |
| 40 mph (64.37 km/h) | 02h 48m |
| 50 mph (80.47 km/h) | 02h 14m |
| 60 mph (96.56 km/h) | 01h 52m |
| 70 mph (112.65 km/h) | 01h 36m |
| 80 mph (129 km/h) | 01h 24m |
Fuel, Round Trip and CO2
Estimated fuel cost and emissions for this route.
| Fuel | $/gal | One way | Round trip |
|---|---|---|---|
| Regular gas | $3.77 | $14.97 | $29.94 |
| Mid-grade | $4.25 | $16.88 | $33.77 |
| Premium | $4.65 | $18.48 | $36.95 |
| Diesel | $5.30 | $21.06 | $42.11 |
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 Illinois · Apr 22, 2026
Distance to Other Cities
Planning a road trip? See the full trip guide on Trip.ovh — stops, fuel costs, weather, and departure timing.