Seoul's subway is one of the finest urban rail systems in the world — 23 lines, 343 stations, a train every 2.5 minutes at peak hours, and coverage so comprehensive that you can reach almost any point in the city without walking more than 10 minutes. For exchange students, mastering it is the single highest-return investment of your first week. Here's everything you actually need to know.

The Basics

Seoul's subway operates from approximately 5:30 AM to midnight, with exact times varying by line and station. Service frequency is every 2–3 minutes on major lines during peak hours (7–9 AM, 6–8 PM), expanding to every 5–7 minutes on off-peak hours.

Fare structure: Distance-based. Most in-city trips cost ₩1,250–₩1,650, charged on your T-Money card. Transfers between subway lines within a single journey are free if made within 30 minutes.

T-Money Card: Your Most Important Possession

The T-Money card (티머니 카드) is a rechargeable transit card that works on every subway line, every city bus, most taxis, and even some convenience stores. Buy one at any subway station ticket machine or convenience store for ₩2,500–₩4,000 (card fee). Load credit at station machines, convenience store counters, or T-Money kiosks — minimum top-up is ₩1,000, maximum balance is ₩500,000.

Why not just use a credit card? Contactless credit cards do work on Seoul transit (Visa and Mastercard), but T-Money gives a small per-ride discount (₩100–₩150 less than cash fare) and makes transfers seamless. Over a semester, this adds up.

Tip: You can register your T-Money card and get a refund on remaining balance if you leave the country — do this at a 7-Eleven before departure.

The Lines You'll Actually Use

You don't need to memorise all 23 lines. These are the ones that matter for exchange students:

Line 2 (녹색, green) — The ring line. Connects Sinchon, Hongdae, Gangnam, Seongsu, and almost every major university district. If you live near Line 2, you can reach most of Seoul without transferring.
Line 3 (주황, orange) — Connects Bukchon (Anguk), Gyeongbokgung, Sinchon, Jongno, and Gangnam south to Suseo. Your palace and traditional Seoul line.
Line 4 (하늘, sky blue) — Runs north-south, connecting Seoul Station, Myeongdong, and the express bus terminal areas.
Line 5 (보라, purple) — Connects Yeouido and further west to east across central Seoul.
Line 6 (갈색, brown) — Korea University (Anam) is on this line; also serves Mapo, Hapjeong, and Itaewon.
Airport AREX — Direct express from Incheon Airport to Seoul Station (43 min, ₩9,500) or all-stop train (60+ min, ₩4,150). Take the express; the time savings are worth the cost.

Exit Numbers: The Hidden System

Every Seoul subway station has multiple exits, and they matter enormously. Major stations have 10, 15, sometimes 20+ exits. In Korea, instead of meeting at "the subway station," people always specify the exit: "홍대입구 9번 출구 앞에서 봐" (meet at Exit 9 of Hongik University station).

Naver Maps shows exit numbers and which exit is closest to your destination — always check before you go up the stairs. Walking to the wrong exit and then back through the station can add 10–15 minutes to a journey.

Navigation Apps

Naver Maps (네이버 지도) — Best overall; shows subway routes, bus options, walking paths, and real-time arrival information. Switch language to English in settings.
Kakao Maps (카카오맵) — Alternative to Naver, similarly accurate, also has English support.
Korea Subway app — Offline subway map with fare calculator; useful when you have no data signal underground.
Google Maps — Works for subway navigation in Seoul, but less accurate for bus routes and sometimes shows outdated exit information.

Unwritten Rules

Stand right, walk left on escalators. This is enforced socially with visible irritation.
Priority seats (노약자석, pink/yellow seats) at the ends of each carriage are reserved for elderly, pregnant, and disabled passengers. Don't sit in them even if the carriage is empty — you'll be asked to move.
Phone calls are technically discouraged in carriages; most Koreans text or use earphones. Speaking loudly is noticed negatively.
Eating and drinking is technically prohibited but widely ignored for coffee cups with lids. Full meals are frowned upon.
Backpacks should be worn on your front during peak hours — standard practice to avoid hitting people with your bag. You'll notice Koreans doing this automatically.

Late Night Transport

The subway stops around midnight. After that, options are: night buses (심야버스) — select routes run through the night at 30–60 minute intervals — or taxis. Seoul taxis are plentiful, metered, and reasonably priced: a 3km trip costs ₩4,800–₩6,000. Use KakaoTaxi app for cashless payment and to avoid the "I don't know where that is" problem. Avoid the black premium taxis at tourist hotspots — they're significantly more expensive.

How to Use Seoul's Subway Like a Local