How far is Longmont, CO from New Castle, CO?
The driving distance from Longmont, CO to New Castle, CO is about 194.2 miles (312.5 km), with a travel time of about 03h 52m by car.
- The straight-line flight distance is about 135.5 miles (218 km).
- For a round trip, plan for roughly 07h 45m 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 52m.
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 Slight Chance Showers And Thunderstorms
Mostly Sunny then Chance Showers And Thunderstorms
Driving Route Map
The map below follows the saved road route between Longmont and New Castle.
Turn-by-Turn Driving Directions
Step-by-step road directions between Longmont and New Castle.
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1
Start on the route
19 m · 10 sec
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2
Turn left onto 5th Avenue
53 m · 10 sec · 5th Avenue
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3
Turn left onto Main Street
17.3 mi · 25 min · Main Street
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4
Continue straight
2797 ft · 1 min
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5
Turn left onto US 36 East: Denver
1737 ft · 44 sec
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6
Merge slight left onto Denver–Boulder Turnpike
1.2 mi · 1 min · Denver–Boulder Turnpike
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7
Keep slight right to continue on Denver–Boulder Turnpike
1.9 mi · 2 min · Denver–Boulder Turnpike
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8
Keep slight right to continue on Denver–Boulder Turnpike
1.2 km · 53 sec · Denver–Boulder Turnpike
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9
Take the exit slight right toward CO 95 South: Sheridan Boulevard
1708 ft · 37 sec
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10
Turn right onto Sheridan Boulevard
4.3 mi · 7 min · Sheridan Boulevard
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11
Take the ramp slight right toward I 76 West
1712 ft · 44 sec
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12
Merge slight left onto Heartland Expressway
1.3 mi · 2 min · Heartland Expressway
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13
Merge slight left
164.2 mi · 3 hr 7 min
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14
Take the exit slight right toward New Castle
1387 ft · 38 sec
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15
Turn right onto Castle Valley Boulevard
553 ft · 9 sec · Castle Valley Boulevard
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16
Enter the roundabout and take exit 3 toward Grand Army of the Republic Highway
77 m · 5 sec · Grand Army of the Republic Highway
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17
Exit the roundabout onto Grand Army of the Republic Highway
2769 ft · 53 sec · Grand Army of the Republic Highway
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18
Continue on East Main Street
3200 ft · 1 min · East Main Street
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19
Turn right onto North 6th Street
144 m · 21 sec · North 6th Street
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20
Arrive at your destination
0 m · 1 sec · North 6th Street
Car Route Details
A richer read on the saved driving route between Longmont and New Castle.
Highway-focused drive
Most of the mileage stays on named highways, so the important moments are ramps, exits, merges, and the final local approach.
Heartland Expressway
Merge slight left
164 mi · 03h 07m
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 Slight Chance Showers And Thunderstorms leaving Longmont and Mostly Sunny then Chance Showers And Thunderstorms near New Castle.
Trip Questions
Direct answers travelers usually want before committing to the drive.
How long does it take to drive from Longmont to New Castle?
The road trip is about 194.2 miles (312.5 km) and usually takes 03h 52m 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 miles from Longmont and 97.2 miles from New Castle.
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 58.7 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 9:14 AM MDT.
How much will gas cost for this route?
Using about 28.3 MPG, regular gas is estimated at $25.33 one way or $50.66 round trip. Estimated CO2 is about 60.9 kg one way.
What should you check before leaving?
Before you leave, expect Mostly Sunny then Slight Chance Showers And Thunderstorms around Longmont and Mostly Sunny then Chance Showers And Thunderstorms near New Castle.
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 Longmont and New Castle. Straight-line distance: 135.47 mi (218.02 km).
#1 Longmont
The most populous city in Boulder County, Colorado.
| Population | 98,445 |
| Coordinates | 40.1672100, -105.1019300 |
| Altitude | 1519 |
| Country | United States |
#2 New Castle
Colorado
| Population | 4,962 |
| Coordinates | 39.5727600, -107.5364400 |
| Altitude | 1706 |
| Country | United States |
End: New Castle (-107.53644, 39.57276)
Estimated Travel Time
Distance: 313 km by road
| Speed | Time |
|---|---|
| 30 mph (48.3 km/h) | 06h 28m |
| 40 mph (64.37 km/h) | 04h 51m |
| 50 mph (80.47 km/h) | 03h 53m |
| 60 mph (96.56 km/h) | 03h 14m |
| 70 mph (112.65 km/h) | 02h 46m |
| 80 mph (129 km/h) | 02h 25m |
Fuel, Round Trip and CO2
Estimated fuel cost and emissions for this route.
| Fuel | $/gal | One way | Round trip |
|---|---|---|---|
| Regular gas | $3.70 | $25.33 | $50.66 |
| Mid-grade | $4.08 | $27.98 | $55.95 |
| Premium | $4.39 | $30.08 | $60.16 |
| Diesel | $4.74 | $32.45 | $64.90 |
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.