How far is New Castle, CO from Boulder, CO?
The driving distance from New Castle, CO to Boulder, CO is about 181.1 miles (291.5 km), with a travel time of about 03h 07m by car.
- The straight-line flight distance is about 124.1 miles (199.7 km).
- For a round trip, plan for roughly 06h 14m of driving time before adding stops, traffic, or weather delays.
- A comfortable departure window is usually 6:00 AM to 8:00 AM MDT.
Reverse, save, or send this route
This drive is better planned with a longer stop or an overnight stay. Copy the route link, send it to another device, or print a clean version before you head out.
This drive is better planned with a longer stop or an overnight stay.
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 03h 07m.
An early departure helps you fit a real stop into the day without turning the return into a late-night drive.
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.
Town in Summit County, Colorado, United States of America
Route Weather Snapshot
Check the forecast at both ends before you head out.
Mostly Sunny
Slight Chance Snow Showers
Driving Route Map
The map below follows the saved road route between New Castle and Boulder.
Turn-by-Turn Driving Directions
Step-by-step road directions between New Castle and Boulder.
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1
Start on North 6th Street
144 m · 26 sec · North 6th Street
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2
Turn left onto West Main Street
3200 ft · 1 min · West Main Street
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3
Continue on Grand Army of the Republic Highway
2784 ft · 53 sec · Grand Army of the Republic Highway
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4
Enter the roundabout and take exit 1 toward Castle Valley Boulevard
4 m · 1 sec · Castle Valley Boulevard
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5
Exit the roundabout onto Castle Valley Boulevard
962 ft · 22 sec · Castle Valley Boulevard
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6
Take the ramp left toward I 70: Denver
1354 ft · 33 sec
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7
Merge slight left
154 mi · 2 hr 58 min
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8
Take the exit slight right toward US 40, I 70 Business East, CH 93: Golden, Morrison
1173 ft · 24 sec
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9
Turn left onto Hogback Road
1123 ft · 35 sec · Hogback Road
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10
Continue on Lariat Loop Scenic Byway
1.1 mi · 2 min · Lariat Loop Scenic Byway
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11
Turn left onto Heritage Road
1415 ft · 29 sec · Heritage Road
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12
Enter the roundabout and take exit 1 toward Heritage Road
32 m · 2 sec · Heritage Road
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13
Exit the roundabout onto Heritage Road
149 m · 10 sec · Heritage Road
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14
Enter the roundabout and take exit 2 toward Heritage Road
15 m · 1 sec · Heritage Road
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15
Exit the roundabout onto Heritage Road
1356 ft · 27 sec · Heritage Road
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16
Enter the roundabout and take exit 2 toward Heritage Road
39 m · 3 sec · Heritage Road
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17
Exit the roundabout onto Heritage Road
707 ft · 16 sec · Heritage Road
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18
Turn slight right onto Heritage Road
809 ft · 20 sec · Heritage Road
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19
Turn left onto Dinosaur Diamond Prehistoric Highway
2.3 mi · 4 min · Dinosaur Diamond Prehistoric Highway
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20
Continue straight
7.5 mi · 11 min
-
21
Continue straight
11.8 mi · 20 min
-
22
Turn right onto University Avenue
1049 ft · 36 sec · University Avenue
-
23
Continue on 17th Street
813 ft · 30 sec · 17th Street
-
24
Turn right onto Athens Street
646 ft · 33 sec · Athens Street
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25
Turn left onto 19th Street
864 ft · 29 sec · 19th Street
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26
Turn left
27 m · 5 sec
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27
Arrive at your destination
0 m · 1 sec
Car Route Details
A richer read on the saved driving route between New Castle and Boulder.
Highway-focused drive
Most of the mileage stays on named highways, so the important moments are ramps, exits, merges, and the final local approach.
I 70
Merge slight left
154 mi · 02h 58m
Route Summary
A quick read on whether this route feels easy, ambitious, or worth planning around.
A longer out-and-back drive
This is still possible in one day, but it becomes a long driving day. Leaving early and planning your stop window matters more here.
Mostly Sunny leaving New Castle and Slight Chance Snow Showers near Boulder.
Trip Questions
Direct answers travelers usually want before committing to the drive.
How long does it take to drive from New Castle to Boulder?
The road trip is about 181.1 miles (291.5 km) and usually takes 03h 07m in normal driving conditions.
Is this a same-day trip or an overnight route?
This is still possible in one day, but it becomes a long driving day. Leaving early and planning your stop window matters more here.
What is the halfway point on this route?
Frisco is a useful midpoint, sitting about 90.1 miles from New Castle and 91 miles from Boulder.
How much longer is the road route than the straight-line distance?
The direct path is about 124.1 miles (199.7 km), while the road route adds roughly 57 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 6:00 AM to 8:00 AM MDT. If you want a more comfortable same-day return, try to leave by 10:46 AM MDT.
How much will gas cost for this route?
Using about 28.3 MPG, regular gas is estimated at $23.63 one way or $47.26 round trip. Estimated CO2 is about 56.8 kg one way.
What should you check before leaving?
Before you leave, expect Mostly Sunny around New Castle and Slight Chance Snow Showers near Boulder.
Stop Ideas Near Frisco
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 Frisco.
Frisco, Colorado
Vail, Colorado
Fairplay, CO
Fraser – Winter Park
Flight Path Map
This map shows the direct air route between New Castle and Boulder. Straight-line distance: 124.11 mi (199.73 km).
#1 New Castle
Colorado
| Population | 4,962 |
| Coordinates | 39.5727600, -107.5364400 |
| Altitude | 1706 |
| Country | United States |
#2 Boulder
The most populous city in Boulder County, Colorado.
| Population | 107,645 |
| Coordinates | 40.0149900, -105.2705500 |
| Altitude | 1624 |
| Country | United States |
End: (-105.27055, 40.014996)
Estimated Travel Time
Distance: 292 km by road
| Speed | Time |
|---|---|
| 30 mph (48.3 km/h) | 06h 02m |
| 40 mph (64.37 km/h) | 04h 31m |
| 50 mph (80.47 km/h) | 03h 37m |
| 60 mph (96.56 km/h) | 03h 01m |
| 70 mph (112.65 km/h) | 02h 35m |
| 80 mph (129 km/h) | 02h 15m |
Fuel, Round Trip and CO2
Estimated fuel cost and emissions for this route.
| Fuel | $/gal | One way | Round trip |
|---|---|---|---|
| Regular gas | $3.70 | $23.63 | $47.26 |
| Mid-grade | $4.08 | $26.10 | $52.19 |
| Premium | $4.39 | $28.06 | $56.12 |
| Diesel | $4.74 | $30.27 | $60.54 |
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 Colorado · Apr 18, 2026
Distance to Other Cities
Planning a road trip? See the full trip guide on Trip.ovh — stops, fuel costs, weather, and departure timing.