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Trip from Federal Way, WA to Mercer Island, WA

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Compiled and reviewed by the US Trip Planner planning team at COD Solutions Oy · Last reviewed Sep 8, 2026 · Editorial standards

Drive Time

37m

Distance

24.7 mi

40 km

Drive Score

7/10

Good drive

Same Day?

Yes, doable

Fuel Cost

$5

one way

EV Charging

Unknown

Best Time to Leave

Save up to 9 min
4 AM
0h 35m ★
6 AM
0h 38m
8 AM
0h 44m
10 AM
0h 40m
12 PM
0h 39m
3 PM
0h 40m
5 PM
0h 44m
8 PM
0h 36m

Estimated drive times based on typical traffic patterns. Actual times may vary with weather, construction, and real-time conditions.

Best Time
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Downtown Federal Way, WA, WA

Federal Way, WA

Wikimedia Commons

Downtown Mercer Island, WA, WA

Mercer Island, WA

JOHN CALLERY

Trip Overview

Federal Way, WA to Mercer Island, WA is 24.7 miles and takes about 37 minutes via I 405 and I 5, with a fuel budget near $5 and enough daylight to finish in a day. This short trip stays within Washington's Pacific Coast region, primarily on major highways. It's a straightforward commute or connection between communities south and east of Seattle. Given the short distance and duration, this route is best suited for a same-day trip, allowing for flexibility in your schedule.

Main Roads

Road Distance Duration
I 405 10.3 mi 12m
I 5 6.9 mi 8m
Pacific Highway South 2.5 mi 4m
South 272nd Street 0.7 mi 1m
I 90 0.5 mi <1m
Southeast 36th Street 0.4 mi 1m
Gallagher Hill Road 0.3 mi <1m
Southeast 40th Street 0.3 mi <1m
Longest stretch: I 405 — 10.3 mi, about 12m

Traffic on I-5

Hour-of-day weekday pattern from 86 FHWA count stations on your route.

Peak

2 PM

~7,288 veh/hr typical

Quietest

1 AM

~803 veh/hr

Peak-to-quiet ratio

9.1×

busier at peak than in the quiet hours

12a 6a noon 6p 11p

Averaged across 105 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 Federal Way, WA and Mercer Island, WA.

1

Start on this road

24 ft · 7 sec · this road
2

Turn left onto South 312th Street

158 ft · 7 sec · South 312th Street
3

Turn right onto WA 99

2.5 mi · 4 min · Pacific Highway South
4

Turn right onto South 272nd Street

0.7 mi · 1 min · South 272nd Street
Use the right lane.
5

Take the ramp

0.4 mi · 54 sec
Toward I-5 North: Seattle Use the left lane.
6

Merge onto I 5

6.9 mi · 8 min · I 5
Use the straight / slight right lanes.
7

Take the exit

448 ft · 10 sec
Exit 154A-B Toward WA 518 West, I 405 North: Seattle-Tacoma International Airport, Bellevue Use the straight / slight right lanes.
8

Keep slight right at fork

0.4 mi · 50 sec
Exit 154B Toward I 405 North: Renton, Bellevue Use the slight right lane.
9

Merge onto I 405

10 mi · 12 min · I 405
Use the straight / slight right lanes.
10

Take the exit

0.2 mi · 31 sec
Exit 11 Toward I 90: Seattle, Spokane Use the straight / slight right lanes.
11

Keep slight left at fork

0.6 mi · 1 min
Toward I 90 West: Seattle
12

Keep slight right at fork

0.4 mi · 55 sec
Toward I 90 West: Seattle, Mercer Island
13

Merge onto I 90

0.5 mi · 36 sec · I 90
14

Take the exit

0.3 mi · 45 sec
Exit 8 Toward East Mercer Way Use the slight right lane.
15

Turn left onto East Mercer Way

332 ft · 11 sec · East Mercer Way
16

Turn sharp right onto Southeast 36th Street

0.4 mi · 1 min · Southeast 36th Street
17

Continue on Gallagher Hill Road

0.3 mi · 43 sec · Gallagher Hill Road
18

Turn right onto Southeast 40th Street

0.3 mi · 46 sec · Southeast 40th Street
19

Turn left onto 86th Avenue Southeast

0.3 mi · 52 sec · 86th Avenue Southeast
Use the left lane.
20

Turn left onto Southeast 42nd Street

0.1 mi · 23 sec · Southeast 42nd Street
21

Arrive at destination

Southeast 42nd Street

Heads-up: tricky spots

5 of 18

5 decision points cluster between mile 3.2 and 23.1 — GPS handles the exact turns, but know they're coming. Your lane choice matters more than the turn itself.

7
3.2 mi into trip | ~6m in

Take the ramp toward I-5 North: Seattle

Lane positioning matters here

Use the left lane. Toward I-5 North: Seattle
8
10.5 mi into trip | ~15m in

Take the exit toward WA 518 West, I 405 North: Seattle-Tacoma International Airport, Bellevue

Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one

Use the straight / slight right lanes. Exit 154A-B Toward WA 518 West, I 405 North: Seattle-Tacoma...
9
10.6 mi into trip | ~16m in

Keep slight right at fork toward I 405 North: Renton, Bellevue

Highway fork - watch signs carefully. Lane positioning matters here. Multiple destination signs - pick the right one

Use the slight right lane. Exit 154B Toward I 405 North: Renton, Bellevue
8
21.3 mi into trip | ~29m in

Take the exit toward I 90: Seattle, Spokane

Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one

Use the straight / slight right lanes. Exit 11 Toward I 90: Seattle, Spokane
7
23.1 mi into trip | ~33m in

Take the exit toward East Mercer Way

Exit ramp - move to the correct lane early. Lane positioning matters here

Use the slight right lane. Exit 8 Toward East Mercer Way

Fuel & Cost

Regular Gas

$5.20 one way

$10.40 round trip

$5.35/gal 25.4 MPG avg 9 kg CO2
Fuel Type $/gal One Way Round Trip
midgrade $5.56 $5.40 $10.81
premium $5.76 $5.60 $11.19
diesel $5.60 $5.44 $10.89

No toll roads detected on this route.

Drive Cost (one way)

Fuel

$5

Estimated CO2 emission: 8.6 kg one way. Prices: EIA weekly data, 2026-08-31.

Driving Electric?

About $3 in charging · 0 stops · 67% less CO2

Vehicle Type kWh Stops DC Fast Home Charge
Average EV 7.4 0 $2.59 $1.19
Efficient EV 6.2 0 $2.16 $0.99
EV Truck/SUV 9.9 0 $3.46 $1.58

Gas CO2

9 kg

EV CO2

3 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.

Forecast as of Aug 26, 2026

Origin

Federal Way, WA

Afternoon in Federal Way on Tuesday

Local time

4:55 PM

PDT

Current temp

78°F

Mostly Sunny

SW 3 to 7 mph 1% chance Live forecast

Fire Weather Watch

Fire Weather Watch issued August 26 at 3:29AM PDT until August 27 at 8:00PM PDT by NWS Spokane WA

Heat Advisory

Heat Advisory issued August 26 at 2:11AM PDT until August 26 at 9:00PM PDT by NWS Spokane WA

Destination

Mercer Island, WA

Afternoon in Mercer Island on Tuesday

Local time

4:55 PM

PDT

Current temp

79°F

Mostly Sunny

SSW 5 mph 1% chance Live forecast

Fire Weather Watch

Fire Weather Watch issued August 26 at 3:29AM PDT until August 27 at 8:00PM PDT by NWS Spokane WA

Heat Advisory

Heat Advisory issued August 26 at 2:11AM PDT until August 26 at 9:00PM PDT by NWS Spokane WA

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

1 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

37m on the road

The weather snapshot is not static. If you are leaving later, give both cities one more quick forecast check before departure.

Weather data from the National Weather Service. Conditions may change; check closer to your travel date.

What kind of drive is this?

This drive is mostly highway, with 72% of the 24.7 miles on major freeways like I 405 and I 5. You'll encounter a longest stretch of 10.3 miles on I 405 before transitioning to surface roads. Expect urban merging and dense exits as you navigate between Federal Way and Mercer Island.

72% highway — fuel and pacing are the main things to plan.
21 navigation steps total — most of the decisions cluster near the start and finish.
Longest single stretch: 10.3 mi on I 405.

How Hard Is This Drive?

10/10

This is a straightforward highway drive that stays mostly on I 405 and I 5. This route has several spots where lane changes, forks, or exits need your full attention. The trickiest moment comes around 3.2 miles in.

Driving Effort 10/10

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 24.7 miles, you will need to pay attention to lane changes and exits — but the whole thing is over in 37m.

Where does it get tricky?

The main spots that need attention: at 3.2 miles: Lane positioning matters here; at 10.5 miles: Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one; at 10.6 miles: Highway fork - watch signs carefully. Lane positioning matters here. Multiple destination signs - pick the right one.

Elevation Profile

Mostly flat terrain

465 ft 16 ft

Total Climb

492 ft

Total Descent

630 ft

Highest Point

465 ft

Elevation Range

448 ft

Towns Mentioned on Route Signs

Based on OSRM destination-sign hints, not a full list of every settlement the road passes.

Between Federal Way, WA and Mercer Island, WA, road signs point toward Bellevue and Spokane.

Bellevue

10.5 mi in | ~15m

Spokane

21.3 mi in | ~29m

About the Cities

Starting in Federal Way, WA

Full guide →

Founded 1929

Federal Way is a city in King County on the Puget Sound of Washington State. It is the home of the Pacific Bonsai Museum and Rhododendron Species Botanical Gardens. With a population of 96,000 (2016), Federal Way is one of Seattle's largest suburbs.

Top landmarks

  • • Wild Waves Theme Park — amusement park and water park in Federal Way, Washington, United States

Arriving in Mercer Island, WA

Full guide →

Mercer Island is a city in King County, Washington, consisting entirely of an island in Lake Washington. Once known as "East Seattle", it has become one of the region's most upscale residential communities.

City content from Wikivoyage (CC BY-SA 4.0) and Wikidata (CC0).

Who Is This Route For?

Weekend Trip

Doable as a same-day drive at 37m. Total distance: 24.7 miles.

Family Friendly

Moderate complexity with 0 natural rest stops along the way.

Solo Traveler

37m drive, comfortable solo distance.

EV Driver

0 DC fast chargers along the route. Coverage: unknown.

First-Time Driver

Mostly highway driving (72%). Some complex stretches to watch for.

Frequently Asked Questions

The longest stretch is about 10.3 miles on I 405. The full list of main roads is in the Roads section above.

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 Mercer Island, WA 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: at 3.2 miles: Lane positioning matters here; at 10.5 miles: Exit ramp - move to the correct lane early. Lane positioning matters here. Multiple destination signs - pick the right one; at 10.6 miles: Highway fork - watch signs carefully. Lane positioning matters here. Multiple destination signs - pick the right one.

Yes — Klondike Gold Rush - Seattle Unit National Historical Park. See the National Parks section for detour distances and tips on detours.

Yes. A round trip is manageable in a single day if you plan a break at Mercer Island, WA 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, EIA for fuel prices, USGS 3DEP for elevation, NPS for national parks, and FHWA TMAS for hourly traffic volumes. See our methodology for refresh cadence and limitations.

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