If you are planning to travel from Saint Peters to Byrnes Mill, you are looking at a straightforward 42.8-mile trip that typically takes about 56 minutes. This route is designed as a one-day excursion, making it an efficient choice for travelers who want to move between these two Missouri locations without the need for an overnight stay. Expect to spend approximately $7 on fuel for the journey, keeping the trip budget-friendly. Because both the origin and destination are situated within the Midwest, the drive maintains a consistent regional feel throughout. It is a highly practical connection that serves as a direct link across the area.
Main Roads
Road
Distance
Duration
I 270
15.6 mi
19m
I 70
13 mi
16m
MO 30
11.1 mi
14m
Upper Byrnes Mill Road
1.4 mi
3m
MO 79
0.1 mi
<1m
Longest stretch:
I 270
— 15.6 mi, about 19m
Turn-by-Turn Driving Directions
Step-by-step road directions between Saint Peters, MO and Byrnes Mill, MO.
1
Start on I 70
1.2 mi·1 min·I 70
2
Take the exit
0.1 mi·15 sec
Exit 220Toward MO 79: Elsberry, LouisianaUse the straight / slight right lanes.
3
Keep slight left at fork
384 ft·14 sec
Toward MO 79
4
Turn left onto MO 79
0.1 mi·11 sec·MO 79
5
Take the ramp
0.2 mi·18 sec
Toward I 70 EastUse the right lane.
6
Merge onto I 70
12 mi·14 min·I 70
Use the straight / slight right lanes.
7
Take the exit
0.2 mi·12 sec
Exit 232Toward I 270: Chicago, MemphisUse the slight right lane.
8
Keep slight right at fork
0.4 mi·33 sec
Toward I 270 South: MemphisUse the slight right lane.
9
Continue on this road
0.1 mi·10 sec·this road
Exit 232Toward I 270 South: Memphis
10
Merge onto I 270
16 mi·19 min·I 270
Use the straight lane.
11
Take the exit
0.3 mi·33 sec
Exit 3Toward MO 30: Gravois RoadUse the slight right lane.
12
Keep slight right at fork
306 ft·7 sec
Toward MO 30 West: FentonUse the right lane.
13
Merge onto MO 30
11 mi·14 min·MO 30
Use the straight lane.
14
Take the exit
109 ft·3 sec
Toward Upper Byrnes Mill Road
15
Turn slight right onto Upper Byrnes Mill Road
1.4 mi·3 min·Upper Byrnes Mill Road
16
Arrive at destination
Upper Byrnes Mill Road
Where to Stop
Rest stops, refuel points, and overnight suggestions along this route.
The midpoint is around 21.4 miles from Saint Peters, MO, which is a good place for a longer meal and fuel stop.
These stop ideas are pacing suggestions — the exact town or exit can change with traffic, hotel plans, and fuel range.
Heads-up: tricky spots
5 of 12
5 decision points cluster between mile 1.2 and 30.2 — GPS handles the exact turns, but know they're coming. Your lane choice matters more than the turn itself.
8
1.2 mi into trip|~1m in
Take the exit toward MO 79: Elsberry, Louisiana
Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one
Use the straight / slight right lanes.
Exit 220
Toward MO 79: Elsberry, Louisiana
8
13.6 mi into trip|~17m in
Take the exit toward I 270: Chicago, Memphis
Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one
Use the slight right lane.
Exit 232
Toward I 270: Chicago, Memphis
7
13.8 mi into trip|~17m in
Keep slight right at fork toward I 270 South: Memphis
Highway fork - watch signs carefully. Lane positioning matters here
Use the slight right lane.
Toward I 270 South: Memphis
7
29.9 mi into trip|~37m in
Take the exit toward MO 30: Gravois Road
Exit ramp - move to the correct lane early. Lane positioning matters here
Use the slight right lane.
Exit 3
Toward MO 30: Gravois Road
8
30.2 mi into trip|~38m in
Keep slight right at fork toward MO 30 West: Fenton
Highway fork - watch signs carefully. Lane positioning matters here
Use the right lane.
Toward MO 30 West: Fenton
Fuel & Cost
Regular Gas
$6.69 one way
$13.38 round trip
$3.97/gal25.4 MPG avg15 kg CO2
Fuel Type
$/gal
One Way
Round Trip
midgrade
$4.36
$7.35
$14.69
premium
$4.89
$8.24
$16.47
diesel
$5.61
$9.45
$18.90
No toll roads detected on this route.
Drive Cost (one way)
Fuel
$7
Estimated CO2 emission: 15 kg one way.
Prices: EIA weekly data, 2026-04-13.
Driving Electric?
About $4 in charging
· 0 stops
· 67% less CO2
Vehicle Type
kWh
Stops
DC Fast
Home Charge
Average EV
12.8
0
$4.49
$2.05
Efficient EV
10.7
0
$3.74
$1.71
EV Truck/SUV
17.1
0
$5.99
$2.74
Gas CO2
15 kg
EV CO2
5 kg (67% less)
This trip is well within single-charge range for most EVs. No charging stops needed if you start fully charged.
DC fast charging avg $0.35/kWh. Home charging avg $0.16/kWh. US grid CO2: 0.39 kg/kWh.
Travel Intel
Current conditions at both ends of the drive.
Forecast as of Apr 14, 2026
Origin
Saint Peters, MO
Late night
in Saint Peters on Sunday
Local time
5:02 AM
CDT
Current temp
66°F
Slight Chance Showers And Thunderstorms
SW 13 mph23% chanceLive forecast
Severe Thunderstorm Warning
Severe Thunderstorm Warning issued April 14 at 3:57AM CDT until April 14 at 4:00AM CDT by NWS St Louis MO
Special Weather Statement
Special Weather Statement issued April 14 at 3:46AM CDT by NWS Quad Cities IA IL
Destination
Byrnes Mill, MO
Late night
in Byrnes Mill on Sunday
Local time
5:02 AM
CDT
Current temp
66°F
Slight Chance Showers And Thunderstorms
SW 9 mph19% chanceLive forecast
Severe Thunderstorm Warning
Severe Thunderstorm Warning issued April 14 at 3:57AM CDT until April 14 at 4:00AM CDT by NWS St Louis MO
Special Weather Statement
Special Weather Statement issued April 14 at 3:46AM CDT by NWS Quad Cities IA IL
Time zone
Same local time
Origin and destination are on the same clock, so arrival timing is easier to judge at a glance.
Temperature spread
Very similar conditions
Both ends of the route are sitting at about the same temperature right now.
Road read
56m on the road
The weather snapshot is not static. If you are leaving later, give both cities one more quick forecast check before departure.
Weather data from the National Weather Service. Conditions may change; check closer to your travel date.
More Details
What kind of drive is this?
This drive is heavily highway-focused, with 93% of the journey taking place on major thoroughfares. You will spend the bulk of your time navigating I-70, I-270, and MO-30 to reach your destination. Be prepared for a standard interstate experience, highlighted by a longest uninterrupted stretch of 15.6 miles on I-270. While the route is efficient, it lacks the technical curves of backroads, functioning instead as a fast-paced transit corridor. You can expect a consistent, predictable rhythm behind the wheel as you transition between these key Missouri highways.
93% highway — fuel and pacing are the main things to plan.
16 navigation steps total — most of the decisions cluster near the start and finish.
Longest single stretch: 15.6 mi on I 270.
How Hard Is This Drive?
10/10
This is a straightforward highway drive that stays mostly on I 270 and I 70. This route has several spots where lane changes, forks, or exits need your full attention. The trickiest moment comes around 1.2 miles in.
Driving Effort10/10
Focused - lots of decisions in a short distance, but it is over quickly
Balances navigation complexity with total wheel time.
This is a short but busy drive. With 12 decision points packed into just 42.8 miles, you will need to pay attention to lane changes and exits — but the whole thing is over in 56m.
Where does it get tricky?
The main spots that need attention: at 1.2 miles: Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one; at 13.6 miles: Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one; at 13.8 miles: Highway fork - watch signs carefully. Lane positioning matters here.
Elevation Profile
Mostly flat terrain
881 ft422 ft
Total Climb
754 ft
Total Descent
728 ft
Highest Point
881 ft
~39.2 mi in
Elevation Range
459 ft
Towns Mentioned on Route Signs
Based on OSRM destination-sign hints, not a full list of every settlement the road passes.
On the drive from Saint Peters, MO to Byrnes Mill, MO, road signs begin pointing toward Memphis along the way.
Memphis
13.6 mi in|~17m
Who Is This Route For?
Weekend Trip
Doable as a same-day drive at 56m. Total distance: 42.8 miles.
Family Friendly
Moderate complexity with 0 natural rest stops along the way.
Solo Traveler
56m drive, comfortable solo distance.
EV Driver
0 DC fast chargers along the route. Coverage: unknown.
First-Time Driver
Mostly highway driving (93%). Some complex stretches to watch for.
Frequently Asked Questions
The longest stretch is about 15.6 miles on I 270. The full list of main roads is in the Roads section above.
It helps. This route has a higher-than-average number of complex decision points, which get harder in the dark. If the last hour of the trip is on surface roads or mountain grades, aim to arrive at Byrnes Mill, MO before sunset when you can. Check the Trip Plan for departure windows that land you in daylight.
Yes. At under 2 hours behind the wheel, this works well for families — plan one quick stop if you have younger kids.
The main spots that need attention: at 1.2 miles: Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one; at 13.6 miles: Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one; at 13.8 miles: Highway fork - watch signs carefully. Lane positioning matters here.
Yes. A round trip is manageable in a single day if you plan a break at Byrnes Mill, MO before heading back.
