Origin
Boulder, CO
Night in Boulder on Saturday
Local time
10:34 PM
MDT
Current temp
72°F
Unavailable
Live forecast
Trip from Boulder, CO to Castlewood, CO
Compiled and reviewed by the US Trip Planner planning team at COD Solutions Oy · Last reviewed Apr 19, 2026 · Editorial standards
Drive Time
56m
Distance
42.4 mi
68 km
Drive Score
8/10
Great drive
Same Day?
Yes, doable
Fuel Cost
$6
one way
EV Charging
Unknown
Best Time to Leave
4 AM
0h 52m
★
6 AM
0h 57m
8 AM
1h 6m
10 AM
1h 0m
12 PM
0h 59m
3 PM
1h 1m
5 PM
1h 6m
8 PM
0h 54m
Estimated drive times based on typical traffic patterns. Actual times may vary with weather, construction, and real-time conditions.
Boulder, CO
Wikimedia Commons
Castlewood, CO
Liudmyla Shalimova
Trip Overview
Boulder, CO to Castlewood, CO is 42.4 miles and takes about 56 minutes via Denver–Boulder Turnpike, with a fuel budget near $6 and enough daylight to finish in a day. This trip stays within the Mountain West region, offering a straightforward drive that's easily manageable in less than an hour. You'll primarily be on well-traveled roads, making it a convenient option for a quick transit or a short day trip. Given its brevity, this route is ideal for those looking to minimize travel time between these two Colorado locations.
Main Roads
| Road | Distance | Duration |
|---|---|---|
| Denver–Boulder Turnpike | 19.7 mi | 23m |
| North Valley Highway | 18.8 mi | 24m |
| 28th Street | 0.8 mi | 1m |
| South Uinta Street | 0.7 mi | 2m |
| Arapahoe Avenue | 0.6 mi | 1m |
| I 25 | 0.4 mi | <1m |
| East Arapahoe Road | 0.4 mi | <1m |
| East Fremont Avenue | 0.2 mi | <1m |
Longest stretch:
Denver–Boulder Turnpike
— 19.7 mi, about 23m
Turn-by-Turn Driving Directions
Step-by-step road directions between Boulder, CO and Castlewood, CO.
1
Start on this road
87 ft
·
6 sec
·
this road
2
Turn right onto 19th Street
143 ft
·
13 sec
·
19th Street
3
Turn left onto Arapahoe Avenue
0.6 mi
·
1 min
·
Arapahoe Avenue
Use the left / straight / right lanes.
4
Turn right onto US 36
0.8 mi
·
1 min
·
28th Street
5
Turn straight onto US 36
3.4 mi
·
4 min
·
Denver–Boulder Turnpike
Use the straight / slight right lanes.
6
Keep slight right at fork onto US 36
1.7 mi
·
1 min
·
Denver–Boulder Turnpike
7
Keep slight right at fork onto US 36
2.6 mi
·
3 min
·
Denver–Boulder Turnpike
8
Keep slight right at fork onto US 36
2.4 mi
·
2 min
·
Denver–Boulder Turnpike
9
Keep slight right at fork onto US 36
2.2 mi
·
2 min
·
Denver–Boulder Turnpike
10
Keep slight right at fork onto US 36
1.9 mi
·
2 min
·
Denver–Boulder Turnpike
11
Keep slight right at fork onto US 36
2.5 mi
·
2 min
·
Denver–Boulder Turnpike
12
Keep slight right at fork onto US 36
2.0 mi
·
2 min
·
Denver–Boulder Turnpike
Use the straight / slight right lanes.
13
Keep slight right at fork onto US 36
1.1 mi
·
1 min
·
Denver–Boulder Turnpike
Toward I 25: Denver, Fort Collins
Use the straight / slight right lanes.
14
Take the exit
0.5 mi
·
47 sec
Toward I 25 south: Denver
Use the straight / slight right lanes.
15
Continue on I 25
0.4 mi
·
33 sec
·
I 25
Toward I 25 south: Denver
16
Merge onto I 25; US 87
19 mi
·
24 min
·
North Valley Highway
Use the straight / slight right lanes.
17
Take the exit onto CO 88
0.2 mi
·
29 sec
·
CO 88
Exit 197
Toward CO 88: Arapahoe Road
Use the straight / slight right lanes.
18
Turn right onto CR 42
0.4 mi
·
46 sec
·
East Arapahoe Road
19
Turn left onto South Uinta Street
0.7 mi
·
2 min
·
South Uinta Street
Use the left lane.
20
At end of road, turn right onto South Tamarac Court
0.1 mi
·
28 sec
·
South Tamarac Court
21
Turn right onto East Fremont Avenue
0.2 mi
·
56 sec
·
East Fremont Avenue
22
Arrive at destination
East Fremont Drive
Where to Stop
Rest stops, refuel points, and overnight suggestions along this route.
Mid-route town
Meal stop
21 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 42 miles helps settle the day before fatigue starts building.
Meal break
The midpoint is around 21.2 miles from Boulder, 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 0 and 40.8 — GPS handles the exact turns, but know they're coming. Your lane choice matters more than the turn itself.
6
0 mi into trip
|
~0m in
|
Arapahoe Avenue
Turn left onto Arapahoe Avenue
Lane positioning matters here
Use the left / straight / right lanes.
6
18 mi into trip
|
~22m 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.
8
20 mi into trip
|
~25m in
|
US 36 / Denver–Boulder Turnpike
Keep slight right at fork onto US 36 / Denver–Boulder Turnpike toward I 25: Denver, Fort Collins
Highway fork - watch signs carefully. Lane positioning matters here. Multiple destination signs - pick the right one
Use the straight / slight right lanes.
Toward I 25: Denver, Fort Collins
6
21.1 mi into trip
|
~26m in
Take the exit toward I 25 south: Denver
Exit ramp - move to the correct lane early. Lane positioning matters here
Use the straight / slight right lanes.
Toward I 25 south: Denver
7
40.8 mi into trip
|
~51m in
|
CO 88
Take the exit onto CO 88 toward CO 88: Arapahoe Road
Exit ramp - move to the correct lane early. Lane positioning matters here
Use the straight / slight right lanes.
Exit 197
Toward CO 88: Arapahoe Road
Fuel & Cost
Regular Gas
$6.39 one way
$12.78 round trip
$3.83/gal
25.4 MPG avg
15 kg CO2
| Fuel Type | $/gal | One Way | Round Trip |
|---|---|---|---|
| midgrade | $4.05 | $6.76 | $13.53 |
| premium | $4.39 | $7.33 | $14.67 |
| diesel | $5.61 | $9.36 | $18.72 |
Estimated Tolls: $1.38
Denver–Boulder Turnpike
(19.7 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
$6
Tolls
$1
Total
$8
Estimated CO2 emission: 14.8 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 | 12.7 | 0 | $4.45 | $2.04 |
| Efficient EV | 10.6 | 0 | $3.71 | $1.70 |
| EV Truck/SUV | 17 | 0 | $5.94 | $2.71 |
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
Castlewood, CO
Night in Castlewood on Saturday
Local time
10:34 PM
MDT
Current temp
77°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 warmer at arrival
A meaningful temperature swing is a good cue to rethink layers, water, and how soon you want to arrive.
Road read
56m 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 presents a mixed drive, with 48% of it on highways. You'll experience a 19.7-mile stretch on the Denver–Boulder Turnpike, which is the longest uninterrupted section. The journey transitions from what's likely urban and suburban environments to potentially more open areas as you approach your destination. Expect a blend of faster highway segments and potentially slower local roads as you navigate through various parts of the Denver metropolitan area.
48% highway, the rest on surface roads — varied driving throughout.
22 navigation steps total — most of the decisions cluster near the start and finish.
Longest single stretch: 19.7 mi on Denver–Boulder Turnpike.
How Hard Is This Drive?
9/10
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 early in the drive near Arapahoe Avenue.
Driving Effort
9/10
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 42.4 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: near the start (Arapahoe Avenue): Lane positioning matters here; at 18 miles (US 36 / Denver–Boulder Turnpike): Highway fork - watch signs carefully. Lane positioning matters here; at 20 miles (US 36 / Denver–Boulder Turnpike): Highway fork - watch signs carefully. Lane positioning matters here. Multiple destination signs - pick the right one.
Towns Mentioned on Route Signs
Based on OSRM destination-sign hints, not a full list of every settlement the road passes.
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 Boulder, CO to Castlewood, CO, road signs begin pointing toward Fort Collins along the way.
Fort Collins
20 mi in
|
~25m
|
via US 36
Who Is This Route For?
Weekend Trip
Doable as a same-day drive at 56m. Total distance: 42.4 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 (48%). Some complex stretches to watch for.
Frequently Asked Questions
The longest stretch is about 19.7 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 Castlewood, 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: near the start (Arapahoe Avenue): Lane positioning matters here; at 18 miles (US 36 / Denver–Boulder Turnpike): Highway fork - watch signs carefully. Lane positioning matters here; at 20 miles (US 36 / Denver–Boulder Turnpike): Highway fork - watch signs carefully. Lane positioning matters here. Multiple destination signs - pick the right one.
Yes. A round trip is manageable in a single day if you plan a break at Castlewood, 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.
Was this helpful?
Thanks for your feedback!
Your tip has been submitted. Thanks!
/500
Recent Tips
·
Explore More
Continue From Castlewood, CO
More trips to Castlewood, CO
Explore more options from Boulder, CO or browse trips ending in Castlewood, CO.
Looking for more statewide routes? Browse CO road trips.