How far is New Castle, CO from Longmont, CO?
The driving distance from New Castle, CO to Longmont, CO is about 202.6 miles (326 km), with a travel time of about 03h 20m by car.
- The straight-line flight distance is about 135.5 miles (218 km).
- For a round trip, plan for roughly 06h 40m 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 20m.
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 then Chance Showers And Thunderstorms
Mostly Sunny then Slight Chance Showers And Thunderstorms
Driving Route Map
The map below follows the saved road route between New Castle and Longmont.
Turn-by-Turn Driving Directions
Step-by-step road directions between New Castle and Longmont.
-
1
Start on North 6th Street
144 m · 26 sec · North 6th Street
-
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
164.2 mi · 3 hr 10 min
-
8
Keep slight left to continue on Heartland Expressway
1.3 mi · 2 min · Heartland Expressway
-
9
Take the exit slight right toward CO 95: Sheridan Boulevard
1606 ft · 40 sec
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10
Turn left onto Sheridan Boulevard
4.6 mi · 8 min · Sheridan Boulevard
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11
Turn left onto US 36 West: Boulder
1765 ft · 37 sec
-
12
Keep slight left to continue on US 36 West
876 ft · 23 sec
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13
Merge slight left onto Denver–Boulder Turnpike
1.5 km · 1 min · Denver–Boulder Turnpike
-
14
Keep slight right to continue on Denver–Boulder Turnpike
1.9 mi · 2 min · Denver–Boulder Turnpike
-
15
Keep slight right to continue on Denver–Boulder Turnpike
1.2 km · 52 sec · Denver–Boulder Turnpike
-
16
Take the exit slight right toward CO 121: Wadsworth Parkway
1951 ft · 42 sec
-
17
Turn right
1257 ft · 30 sec
-
18
Continue straight
5.7 mi · 8 min
-
19
Continue straight
1106 ft · 19 sec
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20
Continue straight
11.5 mi · 16 min
-
21
Turn right onto 5th Avenue
109 m · 20 sec · 5th Avenue
-
22
Turn right onto Kimbark Street
52 m · 9 sec · Kimbark Street
-
23
Turn right
57 m · 16 sec
-
24
Turn right
33 m · 8 sec
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25
Arrive at your destination
0 m · 1 sec
Car Route Details
A richer read on the saved driving route between New Castle and Longmont.
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
164 mi · 03h 10m
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 then Chance Showers And Thunderstorms leaving New Castle and Mostly Sunny then Slight Chance Showers And Thunderstorms near Longmont.
Trip Questions
Direct answers travelers usually want before committing to the drive.
How long does it take to drive from New Castle to Longmont?
The road trip is about 202.6 miles (326 km) and usually takes 03h 20m 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 97.1 miles from New Castle and 105.5 miles from Longmont.
How much longer is the road route than the straight-line distance?
The direct path is about 135.5 miles (218 km), while the road route adds roughly 67.1 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 6:00 AM to 8:00 AM MDT. If you want a more comfortable same-day return, try to leave by 10:20 AM MDT.
How much will gas cost for this route?
Using about 28.3 MPG, regular gas is estimated at $26.44 one way or $52.88 round trip. Estimated CO2 is about 63.5 kg one way.
What should you check before leaving?
Before you leave, expect Mostly Sunny then Chance Showers And Thunderstorms around New Castle and Mostly Sunny then Slight Chance Showers And Thunderstorms near Longmont.
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 Longmont. Straight-line distance: 135.47 mi (218.02 km).
#1 New Castle
Colorado
| Population | 4,962 |
| Coordinates | 39.5727600, -107.5364400 |
| Altitude | 1706 |
| Country | United States |
#2 Longmont
The most populous city in Boulder County, Colorado.
| Population | 98,445 |
| Coordinates | 40.1672100, -105.1019300 |
| Altitude | 1519 |
| Country | United States |
End: (-105.101861, 40.16721)
Estimated Travel Time
Distance: 326 km by road
| Speed | Time |
|---|---|
| 30 mph (48.3 km/h) | 06h 44m |
| 40 mph (64.37 km/h) | 05h 03m |
| 50 mph (80.47 km/h) | 04h 03m |
| 60 mph (96.56 km/h) | 03h 22m |
| 70 mph (112.65 km/h) | 02h 53m |
| 80 mph (129 km/h) | 02h 31m |
Fuel, Round Trip and CO2
Estimated fuel cost and emissions for this route.
| Fuel | $/gal | One way | Round trip |
|---|---|---|---|
| Regular gas | $3.70 | $26.44 | $52.88 |
| Mid-grade | $4.08 | $29.20 | $58.40 |
| Premium | $4.39 | $31.40 | $62.79 |
| Diesel | $4.74 | $33.87 | $67.74 |
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 · Jul 27, 2026
Distance to Other Cities
Planning a road trip? See the full trip guide on Trip.ovh — stops, fuel costs, weather, and departure timing.