交換こうかんする vs. 転換てんかんする: Tips On Correct Word Usage

When you want to say “exchange” or “convert” in Japanese, you’ll encounter two important words: 交換する (koukan suru) and 変換する (henkan suru). At first glance they both involve changing or swapping something, but they operate in very different contexts — and mixing them up can cause real confusion.

Yuka

Rei, I want to say “exchange business cards” and also “convert the file format.” Are these both 交換?

Rei

Good catch! 交換する is for physically exchanging or swapping things — like business cards or gifts. 変換する is for converting or transforming one thing into a different form — like converting a file, changing currency, or transforming data. They’re quite different!

At a Glance: 交換する vs 変換する

交換する (Koukan Suru) — Mutual Exchange

交換する carries the core idea of mutual swapping or reciprocal exchange. The kanji 交 means “to cross / intersect” and 換 means “to trade / swap.” Together they describe a situation where two parties give something to each other, or where one item replaces another equivalent item. It is commonly used for exchanging business cards (名刺交換), swapping contact information, replacing a broken part with a new one, or exchanging gifts.

▶ 名刺を交換しましょう。
Meishi wo koukan shimashou.
Let’s exchange business cards.

▶ タイヤを交換する必要がある。
Taiya wo koukan suru hitsuyou ga aru.
I need to replace (swap out) the tires.

▶ 彼女とLINEを交換した。
Kanojo to LINE wo koukan shita.
I exchanged LINE contact info with her.

Yuka

So 交換する is like swapping — two things moving between two people or two places?

Rei

Exactly! Think of the 交 in 交換 — it means “crossing,” like two things crossing paths between two parties.

変換する (Henkan Suru) — Conversion and Transformation

変換する uses the kanji 変 (change) and 換 (swap/convert). It describes the process of changing something from one form or state into another — not necessarily involving two parties. You use it for technical conversions (file formats, data encoding), transforming text input on computers (kana to kanji conversion), or converting one type of thing into another equivalent. In Japan, typing Japanese on a keyboard involves 変換 — you type in romaji or hiragana and press the conversion key.

▶ このファイルをPDFに変換してください。
Kono fairu wo PDF ni henkan shite kudasai.
Please convert this file to PDF.

▶ ひらがなを漢字に変換する。
Hiragana wo kanji ni henkan suru.
Convert hiragana to kanji (on a computer/IME).

▶ エネルギーを電力に変換する技術。
Enerugii wo denryoku ni henkan suru gijutsu.
Technology for converting energy into electrical power.

Yuka

Oh! So every time I press the space bar to convert kana to kanji on my keyboard, that’s 変換 happening?

Rei

Exactly right! The key on Japanese keyboards is literally called the 変換キー (henkan kii) — the conversion key. Great connection!

Common Mistakes

Side-by-Side Comparison

Additional Usage: Related Vocabulary

Decision Flowchart

Are you swapping or changing something?
         |
         v
Is it a mutual exchange between two parties (people/things)?
  YES → 交換する ✅ (e.g., business cards, contact info, parts)
  NO  ↓
Are you transforming something from one form to another?
  YES → 変換する ✅ (e.g., file format, kana→kanji, data)
Is it currency? → 両替する is more natural ✅
Is it a policy/direction shift? → 転換する ✅

Quick Quiz

Yuka

I think I’ve got it. Can I try the quiz?

Rei

Go for it! Choose 交換する or 変換する.

Q1. “I need to swap out the batteries.”
電池を___ → 交換する ✅

Q2. “Please convert this audio file to MP3.”
このオーディオファイルをMP3に___ → 変換する ✅

Q3. “We exchanged email addresses.”
メールアドレスを___ → 交換した ✅

Q4. “The IME converts my input to kanji.”
入力を漢字に___ → 変換する ✅

Q5. “I want to replace my old phone.”
古いスマホを新しいものに___ → 交換する ✅

＼ Learn Japanese with a personal native teacher!／

あわせて読みたい

あわせて読みたい

chuumon-vs-irai In a Japanese restaurant, you ちゅうもんする (order) your food. When you need a colleague to do something for you, you make an いらい (request). Both words i...

あわせて読みたい

hatsubai-vs-hanbai A new video game just came out. Is that 発売 or 販売? Your local convenience store sells snacks every day — is that 発売 or 販売? Both words involve selling ...