Post Falls to Ammon is 491.3 miles and takes about 8 hours 9 minutes via I 90 and I 15, with a fuel budget near $87 and enough daylight to finish in a day if you start early. This trip stays within Idaho, traversing the Mountain West region for its entirety. It's a largely highway drive, making it a straightforward option for a single-day push or a relaxed two-day excursion. You'll spend most of your time on major interstates, so plan for efficient travel.
Trip Pace
Best split across 2 days
Treat the return leg as its own travel day rather than an afterthought.
Break Rhythm
2 planned breaks
Plan on a short reset every 3 to 4 hours to stay fresh behind the wheel.
Midpoint
245.6 miles from Post Falls, ID
A natural place for your longest stop of the day
, about 4h 9m into the drive
.
Main Roads
Road
Distance
Duration
I 90
285.1 mi
4h 47m
I 15
198 mi
3h 5m
East Sunnyside Road
2.9 mi
4m
West 17th Street
1.1 mi
1m
South Holmes Avenue
1 mi
1m
South Utah Avenue
0.6 mi
1m
West Broadway Street
0.4 mi
<1m
North Spokane Street
0.4 mi
1m
Longest stretch:
I 90
— 285.1 mi, about 4h 47m
Traffic on I-90
Hour-of-day weekday pattern from 58 FHWA count stations on your route.
Peak
4 PM
~981 veh/hr typical
· worst 1,230
Quietest
2 AM
~52 veh/hr
Peak-to-quiet ratio
18.9×
busier at peak than in the quiet hours
12a6anoon6p11p
Averaged across 52 weeks of 2023 FHWA Travel Monitoring Analysis System data. Weekday hours only (Mon–Fri).
Turn-by-Turn Driving Directions
Step-by-step road directions between Post Falls, ID and Ammon, ID.
1
Start on West 10th Avenue
0.2 mi·40 sec·West 10th Avenue
2
Turn right onto North Spokane Street
0.4 mi·1 min·North Spokane Street
3
Turn left
0.4 mi·51 sec
4
Merge onto I 90
285 mi·4 hr 47 min·I 90
5
Take the exit
0.5 mi·1 min
Toward I 15 South: Dillon, Idaho Falls
6
Merge onto I 15
198 mi·3 hr 5 min·I 15
7
Take the exit onto I 15 BUS; US 20
0.3 mi·46 sec·I 15 BUS; US 20
Toward I 15 Business, US 20 West: Historic Downtown, Arco
8
Continue on I 15 BUS; US 20
0.4 mi·54 sec·West Broadway Street
9
Turn right onto South Utah Avenue
0.5 mi·50 sec·South Utah Avenue
10
Enter roundabout onto South Utah Avenue
103 ft·2 sec·South Utah Avenue
11
Continue on South Utah Avenue
0.1 mi·23 sec·South Utah Avenue
12
Turn left onto Pancheri Drive
0.4 mi·42 sec·Pancheri Drive
13
Continue on West 17th Street
1.1 mi·1 min·West 17th Street
14
Turn right onto South Holmes Avenue
1.0 mi·1 min·South Holmes Avenue
15
Turn left onto East Sunnyside Road
2.9 mi·4 min·East Sunnyside Road
16
Turn left onto Central Avenue
0.1 mi·35 sec·Central Avenue
17
Turn right onto Molen Street
135 ft·6 sec·Molen Street
18
Arrive at destination
Molen Street
Trip Plan
For an 8-hour drive, starting early in Post Falls is recommended to maximize daylight. While it's possible to complete this route in one day, splitting it into two days with an overnight stop would make for a more relaxed pace. You have two suggested stops along the way, which are good opportunities to refuel and stretch your legs. Keep an eye on your fuel level, especially during the 285.1-mile segment on I 90, as services can be spread out in some sections.
Morning Departure
Start early — leave by 6-7 AM to arrive at a reasonable hour.
Evening Departure
This is a long drive — plan for a morning departure or consider splitting it into two days.
This drive is better paced as a 2-day trip.
Plan roughly 2 meaningful breaks for fuel, food, and rest.
The halfway point lands around 245.6 miles from Post Falls, ID, or about 4h 9m into the drive.
The longest continuous stretch on this route runs about 285.1 miles.
Consider an overnight stop or starting very early.
Departure
Before you leave
Start with fuel, water, and navigation already sorted so the first hour feels easy.
First stop
Around 108 miles or 1h 50m in
Use this first pause for coffee, a restroom break, and a quick traffic check ahead.
Halfway reset
Around 245.6 miles or 4h 9m in
This is the best place for your longest stop, a real meal, and a full fuel check.
Overnight split
Day 1 wrap after about 245.6 miles or 4h 9m
Stop before fatigue turns the last few hours into a grind. You want day two to start fresh, not just resumed.
Final approach
Final hour starts around 7h 7m
Traffic, exits, and arrival timing usually matter more near Ammon, ID than in the middle of the route.
Before You Leave
+
Open the route before leaving Post Falls, ID so your first major turns are already loaded.
+
Leave with enough water and a charging cable within reach, not packed away.
+
Check your fuel range against the first long segment, especially if you are starting outside city service areas.
+
Pick one backup stop option before the midpoint in case traffic changes your pacing.
+
Treat this as a 2-day road trip and book the overnight stop before the busiest arrival window.
Day 1
Settle into the route from Post Falls, ID
Aim for roughly 246 miles and 4.1 hours of wheel time on this day.
Day 2
Finish the approach into Ammon, ID
Aim for roughly 246 miles and 4.1 hours of wheel time on this day.
Your first comfortable stop window is around 108 miles from Post Falls, ID.
This route usually feels better as a 2-day drive than as one long push.
Plan about 2 real breaks rather than only quick fuel stops.
The longest stretch is on I 90 for about 285.1 miles.
Where to Stop
Rest stops, refuel points, and overnight suggestions along this route.
Place data sourced from public business listings. Hours and availability may vary.
Heads-up: tricky spots
5 of 14
5 decision points cluster between mile 0.2 and 491.3 — GPS handles the exact turns, but know they're coming. Your lane choice matters more than the turn itself.
4
0.2 mi into trip|~0m in|North Spokane Street
Turn right onto North Spokane Street
Navigation decision point
5
286 mi into trip|~4h 50m in
Take the exit toward I 15 South: Dillon, Idaho Falls
Exit ramp - move to the correct lane early. Multiple destination signs - pick the right one
Toward I 15 South: Dillon, Idaho Falls
5
484.5 mi into trip|~7h 57m in|I 15 BUS; US 20
Take the exit onto I 15 BUS; US 20 toward I 15 Business, US 20 West: Historic Downtown, Arco
Exit ramp - move to the correct lane early. Multiple destination signs - pick the right one
Toward I 15 Business, US 20 West: Historic Down...
4
485.2 mi into trip|~7h 59m in|South Utah Avenue
Turn right onto South Utah Avenue
Navigation decision point
5
491.3 mi into trip|~8h 9m in|Molen Street
Turn right onto Molen Street
Navigation decision point
Fuel & Cost
Regular Gas
$76.58 one way
$153.15 round trip
$3.96/gal25.4 MPG avg172 kg CO2
Fuel Type
$/gal
One Way
Round Trip
midgrade
$4.17
$80.72
$161.43
premium
$4.47
$86.54
$173.08
diesel
$4.80
$92.77
$185.53
No toll roads detected on this route.
Estimated Trip Cost (one way, 1 person)
Fuel
$77
Hotel (1n)
$80–$140
Meals
$50–$100
Total
$207–$317
Rough estimate based on US averages. Hotel $80–$140/night, meals $25–$50/day.
Estimated CO2 emission: 171.9 kg one way.
Prices: EIA weekly data, 2026-07-13.
Driving Electric?
About $52 in charging
· 1 stop
· 67% less CO2
Vehicle Type
kWh
Stops
DC Fast
Home Charge
Average EV
147.4
1
$51.59
$23.58
Efficient EV
122.8
1
$42.99
$19.65
EV Truck/SUV
196.5
2
$68.78
$31.44
Gas CO2
172 kg
EV CO2
57 kg (67% less)
Plan for 1 charging stop. A 30-minute DC fast charge mid-route should be enough to complete the trip comfortably.
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.
Forecast as of Jul 16, 2026
Origin
Post Falls, ID
Evening
in Post Falls on Saturday
Local time
6:26 PM
PDT
Current temp
100°F
Slight Chance Showers And Thunderstorms
E 3 mph29% chanceLive forecast
Severe Thunderstorm Warning
Severe Thunderstorm Warning issued July 16 at 3:43PM PDT until July 16 at 4:15PM PDT by NWS Spokane WA
Special Weather Statement
Special Weather Statement issued July 16 at 4:36PM MDT by NWS Boise ID
Destination
Ammon, ID
Evening
in Ammon on Saturday
Local time
7:26 PM
MDT
Current temp
92°F
Slight Chance Showers And Thunderstorms
ESE 5 mph17% chanceLive forecast
Severe Thunderstorm Warning
Severe Thunderstorm Warning issued July 16 at 3:43PM PDT until July 16 at 4:15PM PDT by NWS Spokane WA
Special Weather Statement
Special Weather Statement issued July 16 at 4:36PM MDT by NWS Boise ID
Seasonal Notes
Summer travel usually means heavier construction, hotter rest stops, and busier weekend traffic around major cities.
Winter travel shortens daylight, so a route that looks manageable on paper can feel much longer after dark.
Holiday weekends tend to make both departure and arrival windows slower than the raw route time suggests.
For long drives, weather on day two can matter just as much as conditions at departure, so check the whole travel window rather than only the first day.
Time zone
1 hour later
The destination clock does not match departure time, so double-check hotel check-in windows and late arrival plans.
Temperature spread
8 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
8h 9m on the road
This is long enough that the arrival forecast matters almost as much as departure conditions. Recheck both ends before you roll.
Weather data from the National Weather Service. Conditions may change; check closer to your travel date.
More Details
What kind of drive is this?
This drive is 98% highway, meaning you'll be on interstates for almost the entire 491.3 miles. The longest uninterrupted stretch is 285.1 miles on I 90. You'll transition to surface roads, specifically East Sunnyside Road, closer to your destination. Expect consistent cruising speeds for the bulk of the trip, with the potential for merging traffic as you approach populated areas near the end.
98% highway — fuel and pacing are the main things to plan.
18 navigation steps total — most of the decisions cluster near the start and finish.
Longest single stretch: 285.1 mi on I 90.
How Hard Is This Drive?
4/10
This is a straightforward highway drive that stays mostly on I 90 and I 15. There are only a few real navigation decisions along the way. The trickiest moment comes around 0.2 miles in near North Spokane Street.
Driving Effort4/10
Easy - simple navigation with a manageable amount of wheel time
Balances navigation complexity with total wheel time.
The route itself is not hard, but at 8h 9m, endurance matters. Plan breaks every 2-3 hours. The 14 decision points are all manageable with basic attention.
Where does it get tricky?
The main spots that need attention: at 0.2 miles (North Spokane Street): Navigation decision point; at 286 miles: Exit ramp - move to the correct lane early. Multiple destination signs - pick the right one; at 484.5 miles (I 15 BUS; US 20): Exit ramp - move to the correct lane early. Multiple destination signs - pick the right one.
Elevation Profile
High-altitude sections with notable climbs
6,049 ft2,153 ft
Total Climb
5,701 ft
Total Descent
3,162 ft
Highest Point
6,049 ft
~388 mi in
Elevation Range
3,896 ft
Notable High Points
4,487 ft at ~70.5 miles+1,647 ft prominence
5,410 ft at ~282.1 miles+147 ft prominence
6,049 ft at ~388 miles+120 ft prominence
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 Post Falls, ID to Ammon, ID, road signs begin pointing toward Idaho Falls along the way.
The longest stretch is about 285.1 miles on I 90. The full list of main roads is in the Roads section above.
Yes — a 2-day pace is more comfortable than one long haul. A sensible stopping point is after roughly 246 miles on day one.
Yes — we found about 24 rest areas or service plazas within a short detour of the route (from OpenStreetMap). See the Rest Stops tab under Nearby Places for locations and mile markers. Plan to stretch, use the bathroom, and top off fluids every 2–3 hours on longer drives.
It helps. This is a long drive, so arriving tired and in the dark compounds. If the last hour of the trip is on surface roads or mountain grades, aim to arrive at Ammon, ID before sunset when you can. Check the Trip Plan for departure windows that land you in daylight.
Only with planning. This is a long drive for kids — consider splitting it into two days rather than pushing through. Plan at least 2 meaningful breaks. There are 24 rest areas along the route for bathroom stops.
Mostly yes along the main roads, but rural stretches through ID can have sparse or no coverage. Before you leave, download offline Google Maps or Apple Maps for the route, and consider downloading music or podcasts instead of streaming. If you depend on data for navigation, keep a paper backup of the turn-by-turn directions.
The main spots that need attention: at 0.2 miles (North Spokane Street): Navigation decision point; at 286 miles: Exit ramp - move to the correct lane early. Multiple destination signs - pick the right one; at 484.5 miles (I 15 BUS; US 20): Exit ramp - move to the correct lane early. Multiple destination signs - pick the right one.
Not recommended in a single day. At 8.2 hours each way, a round trip means 16.3 hours of driving — that is an unsafe level of fatigue for most drivers. Plan at least one night at Ammon, ID before the return drive.
