Origin
Castlewood, CO
Night in Castlewood on Saturday
Local time
10:34 PM
MDT
Current temp
77°F
Unavailable
Live forecast
Trip from Castlewood, CO to Boulder, CO
Compiled and reviewed by the US Trip Planner planning team at COD Solutions Oy · Last reviewed Apr 19, 2026 · Editorial standards
Drive Time
57m
Distance
43.5 mi
70 km
Drive Score
8/10
Great drive
Same Day?
Yes, doable
Fuel Cost
$7
one way
EV Charging
Unknown
Best Time to Leave
4 AM
0h 53m
★
6 AM
0h 58m
8 AM
1h 7m
10 AM
1h 1m
12 PM
1h 0m
3 PM
1h 2m
5 PM
1h 7m
8 PM
0h 55m
Estimated drive times based on typical traffic patterns. Actual times may vary with weather, construction, and real-time conditions.
Castlewood, CO
Liudmyla Shalimova
Boulder, CO
Wikimedia Commons
Trip Overview
Castlewood, CO to Boulder, CO is 43.5 miles and takes about 57 minutes via Denver–Boulder Turnpike, with a fuel budget near $7 and enough daylight to finish in a day. This relatively short trip connects two points within the Mountain West region, offering a straightforward drive. You'll primarily be on highway routes, making it an efficient option for getting between these Colorado locations. Consider this route if you need a quick and predictable journey with minimal time commitment. It’s a good choice for a same-day excursion or a brief leg of a larger trip.
Main Roads
| Road | Distance | Duration |
|---|---|---|
| Denver–Boulder Turnpike | 19.8 mi | 23m |
| South Valley Highway | 19.5 mi | 24m |
| East Arapahoe Road | 1.1 mi | 1m |
| South Quebec Street | 0.8 mi | 1m |
| 28th Street | 0.8 mi | 1m |
| Arapahoe Avenue | 0.6 mi | 1m |
| East Fremont Drive | 0.1 mi | <1m |
| East Hinsdale Avenue | <0.1 mi | <1m |
Longest stretch:
Denver–Boulder Turnpike
— 19.8 mi, about 23m
Turn-by-Turn Driving Directions
Step-by-step road directions between Castlewood, CO and Boulder, CO.
1
Start on East Fremont Drive
0.1 mi
·
33 sec
·
East Fremont Drive
2
Turn right onto East Hinsdale Avenue
497 ft
·
24 sec
·
East Hinsdale Avenue
3
At end of road, turn right onto South Quebec Street
0.8 mi
·
1 min
·
South Quebec Street
4
Turn right onto CR 42
1.1 mi
·
1 min
·
East Arapahoe Road
Use the right lane.
5
Take the ramp
0.2 mi
·
23 sec
Toward I 25 North: Denver
6
Merge onto I 25
19 mi
·
24 min
·
South Valley Highway
Use the straight / slight right lanes.
7
Take the exit
0.6 mi
·
51 sec
Exit 217A
Toward US 36 West: Westminster, Boulder
Use the slight left lane.
8
Merge onto US 36
2.1 mi
·
2 min
·
Denver–Boulder Turnpike
9
Keep slight right at fork onto US 36
1.7 mi
·
1 min
·
Denver–Boulder Turnpike
10
Keep slight right at fork onto US 36
2.3 mi
·
2 min
·
Denver–Boulder Turnpike
11
Keep slight right at fork onto US 36
1.9 mi
·
2 min
·
Denver–Boulder Turnpike
Use the straight / slight right lanes.
12
Keep slight right at fork onto US 36
2.1 mi
·
2 min
·
Denver–Boulder Turnpike
Use the straight / slight right lanes.
13
Keep slight right at fork onto US 36
2.9 mi
·
3 min
·
Denver–Boulder Turnpike
Use the straight / slight right lanes.
14
Keep slight right at fork onto US 36
2.4 mi
·
2 min
·
Denver–Boulder Turnpike
Use the straight / slight right lanes.
15
Keep slight right at fork onto US 36
2.2 mi
·
2 min
·
Denver–Boulder Turnpike
16
Keep slight left at fork onto US 36
2.3 mi
·
2 min
·
Denver–Boulder Turnpike
Use the straight lane.
17
Continue on US 36
0.8 mi
·
1 min
·
28th Street
Use the left / straight lanes.
18
Turn left onto Arapahoe Avenue
0.6 mi
·
1 min
·
Arapahoe Avenue
Use the left lane.
19
Turn right onto 19th Street
143 ft
·
11 sec
·
19th Street
Use the straight / right lanes.
20
Turn left
87 ft
·
4 sec
21
Arrive at destination
Where to Stop
Rest stops, refuel points, and overnight suggestions along this route.
Mid-route town
Meal stop
22 mi into the route
Best for: Lunch, fuel, and a longer reset
This sits close to the middle of the route, so it works well for the longest stop of the day.
Pacing Suggestions
Fuel and coffee
A short stop after about 10 miles helps settle the day before fatigue starts building.
Meal break
The midpoint is around 21.8 miles from Castlewood, CO, 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 185 decision points cluster between mile 1 and 32.3 — GPS handles the exact turns, but know they're coming. Your lane choice matters more than the turn itself.
6
1 mi into trip
|
~2m in
|
CR 42 / East Arapahoe Road
Turn right onto CR 42 / East Arapahoe Road
Lane positioning matters here
Use the right lane.
8
21.8 mi into trip
|
~30m in
Take the exit toward US 36 West: Westminster, Boulder
Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one
Use the slight left lane.
Exit 217A
Toward US 36 West: Westminster, Boulder
6
28.3 mi into trip
|
~37m in
|
US 36 / Denver–Boulder Turnpike
Keep slight right at fork onto US 36 / Denver–Boulder Turnpike
Highway fork - watch signs carefully. Lane positioning matters here
Use the straight / slight right lanes.
6
30.2 mi into trip
|
~40m in
|
US 36 / Denver–Boulder Turnpike
Keep slight right at fork onto US 36 / Denver–Boulder Turnpike
Highway fork - watch signs carefully. Lane positioning matters here
Use the straight / slight right lanes.
6
32.3 mi into trip
|
~42m in
|
US 36 / Denver–Boulder Turnpike
Keep slight right at fork onto US 36 / Denver–Boulder Turnpike
Highway fork - watch signs carefully. Lane positioning matters here
Use the straight / slight right lanes.
Fuel & Cost
Regular Gas
$6.55 one way
$13.11 round trip
$3.83/gal
25.4 MPG avg
15 kg CO2
| Fuel Type | $/gal | One Way | Round Trip |
|---|---|---|---|
| midgrade | $4.05 | $6.94 | $13.88 |
| premium | $4.39 | $7.53 | $15.05 |
| diesel | $5.61 | $9.60 | $19.21 |
Estimated Tolls: $1.38
Denver–Boulder Turnpike
(19.8 mi)
$1.38
Toll estimates based on average 2024-2025 rates. EZ-Pass/SunPass discounts may lower the actual cost.
Drive Cost (one way)
Fuel
$7
Tolls
$1
Total
$8
Estimated CO2 emission: 15.2 kg one way. Prices: EIA weekly data, 2026-04-13.
Driving Electric?
About $5 in charging · 0 stops · 67% less CO2
| Vehicle Type | kWh | Stops | DC Fast | Home Charge |
|---|---|---|---|---|
| Average EV | 13 | 0 | $4.57 | $2.09 |
| Efficient EV | 10.9 | 0 | $3.81 | $1.74 |
| EV Truck/SUV | 17.4 | 0 | $6.09 | $2.78 |
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.
Destination
Boulder, CO
Night in Boulder on Saturday
Local time
10:34 PM
MDT
Current temp
72°F
Unavailable
Live forecast
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
5 degrees cooler at arrival
A meaningful temperature swing is a good cue to rethink layers, water, and how soon you want to arrive.
Road read
57m on the road
Use the two city cards together: check the sky where you start, then compare it with the local time and temperature at arrival.
Weather data from the National Weather Service. Conditions may change; check closer to your travel date.
What kind of drive is this?
This route features a mixed drive profile, with 45% of the journey on highways. You'll experience stretches of faster travel, including a longest uninterrupted stretch of 19.8 miles on the Denver–Boulder Turnpike. The drive will likely transition between more developed highway sections and potentially more local road segments as you approach your destination. Expect a dynamic driving experience that balances efficiency with the character of Colorado roadways. The road's personality shifts subtly, offering varied conditions to keep you engaged.
45% highway, the rest on surface roads — varied driving throughout.
21 navigation steps total — most of the decisions cluster near the start and finish.
Longest single stretch: 19.8 mi on Denver–Boulder Turnpike.
How Hard Is This Drive?
10/10
This route mixes highway mileage with some local-road sections near the start or finish. This route has several spots where lane changes, forks, or exits need your full attention. The trickiest moment comes around 1 miles in near CR 42 / East Arapahoe Road.
Driving Effort
10/10
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 18 decision points packed into just 43.5 miles, you will need to pay attention to lane changes and exits — but the whole thing is over in 57m.
Where does it get tricky?
The main spots that need attention: at 1 miles (CR 42 / East Arapahoe Road): Lane positioning matters here; at 21.8 miles: Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one; at 28.3 miles (US 36 / Denver–Boulder Turnpike): Highway fork - watch signs carefully. Lane positioning matters here.
Who Is This Route For?
Weekend Trip
Doable as a same-day drive at 57m. Total distance: 43.5 miles.
Family Friendly
Moderate complexity with 0 natural rest stops along the way.
Solo Traveler
57m drive, comfortable solo distance.
EV Driver
0 DC fast chargers along the route. Coverage: unknown.
First-Time Driver
Mostly highway driving (45%). Some complex stretches to watch for.
Frequently Asked Questions
The longest stretch is about 19.8 miles on Denver–Boulder Turnpike. The full list of main roads is in the Roads section above.
Expect about $1.38 in tolls one way, starting with Denver–Boulder Turnpike. Most Northeast and Midwest toll agencies accept E-ZPass; in the West and Texas, transponders like TxTag or FasTrak apply. If you do not have a transponder, cashless tolling plates will mail a bill to the vehicle's registered address — usually with a surcharge, so a rental-car toll pass is often cheaper than paying by mail.
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 Boulder, CO 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 miles (CR 42 / East Arapahoe Road): Lane positioning matters here; at 21.8 miles: Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one; at 28.3 miles (US 36 / Denver–Boulder Turnpike): 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 Boulder, CO before heading back.
How this page is built
Compiled by the US Trip Planner planning team at COD Solutions Oy from open government datasets — OSRM over OpenStreetMap for geometry, and EIA for fuel prices. See our methodology for refresh cadence and limitations.
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