How to study kanji: how many you need, radicals, readings and spaced repetition

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Kanji are the part of Japanese that intimidates people most, and the part that rewards a good method most. There are a lot of them, each can have several readings, and many look alike. But kanji are built from a limited set of parts, and once you see the patterns, learning new ones gets faster. Here is how to approach them.

How many kanji do you need?

The Japanese government's Jōyō kanji list, the characters for general use in newspapers, official documents and school, has 2,136 characters since its 2010 revision. Of those, 1,006 are taught in primary school (the kyōiku kanji), and the rest in secondary school. You do not need all of them to start reading. A few hundred well-chosen kanji cover a large share of everyday text, and knowing around 1,000 lets you get through a lot of real material with a dictionary. The full Jōyō list is a long-term goal for reading newspapers and novels comfortably.

Kanji and the JLPT

The Japanese-Language Proficiency Test (JLPT) has five levels, N5 (easiest) to N1. Since the test was revised in 2010, the organisers have not published official kanji or vocabulary lists for each level, on the grounds that the test measures communication rather than memorised lists. The level lists you find in textbooks and apps are estimates based on older lists and past papers. As a rough guide, N5 needs around a hundred basic kanji and N1 expects most of the Jōyō list, but treat any exact number with caution.

Radicals: the building blocks

Most kanji are made of smaller components, called radicals or simply parts.

氵 (water) appears in 海 (sea), 泳 (swim), 洗 (wash).
亻 (person) appears in 休 (rest), 体 (body), 作 (make).
木 (tree) appears in 林 (grove), 森 (forest), 机 (desk).

Learning the common components first means a new kanji is no longer twenty random strokes but three parts you already know. Many kanji also have a part that hints at the on-reading, such as 青, 晴, 清 and 精, all read sei.

On and kun readings

Most kanji have two kinds of reading:

On'yomi (音読み): derived from Chinese, usually used in compound words. 山 in 富士山 is read san.
Kun'yomi (訓読み): the native Japanese reading, usually used when the kanji stands alone or with kana endings. 山 on its own is yama.

A useful rule of thumb: two or more kanji together usually take on-readings; a kanji followed by hiragana usually takes a kun-reading. There are many exceptions, which is why the best approach is the next point.

Learn kanji through vocabulary

Memorising every reading of a kanji in isolation is slow and easy to forget. Learn words instead, and the readings come with them:

学 in 学生 (gakusei, student), 大学 (daigaku, university), 学ぶ (manabu, to learn).
生 in 先生 (sensei), 生きる (ikiru, to live), 生まれる (umareru, to be born).

Choose words you actually meet in your textbook, games, songs or dramas, and you will see the kanji again in context, which is what makes them stick.

Spaced repetition

Spaced repetition software shows you each item just before you are likely to forget it, so you spend time on what you do not know yet. Anki (free, with shared decks or your own cards) and kanji-specific apps both work this way.

Keep daily new cards small and steady, such as 5 to 15 kanji or words a day.
Do your reviews every day; a missed week builds a pile that is hard to clear.
Put the word, its reading and an example sentence on the card, not just the kanji and an English keyword.

Writing by hand

You do not need to hand-write every kanji fluently to read them, and most people type Japanese on a phone or computer. But writing a new kanji a few times, in the right stroke order, helps you notice its parts and tell look-alikes apart (such as 未 and 末, or 待 and 持).

A simple weekly routine

Learn the components of a handful of new kanji.
Add five to ten words that use them to your spaced repetition deck.
Read something graded or simple every day, and look up kanji you meet more than once.
Review mistakes at the end of the week.

How many kanji do you know, and what method has worked for you? Share your tips or ask for advice in the comments.