Translation guide
The English word 'thickness' refers to the dimension of an object from one surface to the opposite, or the quality of being thick. In Japanese, the most common equivalent is 厚さ (atsusa), but the appropriate word depends on what is being described: flat objects, cylindrical objects, liquids, or abstract density.
Describing the dimension between two parallel surfaces of a flat object.
The standard word for thickness of flat things like boards, walls, books, or slices. It is a noun derived from the adjective 厚い (atsui, 'thick').
The thickness of this board is 2 centimeters.
壁の厚さを測ってください。
Please measure the thickness of the wall.
Similar to 厚さ, but often implies a sense of substantial thickness or volume, and can be used more subjectively. Common in everyday speech.
このステーキは厚みがあって美味しそうだ。
This steak looks delicious with its thickness.
Describing the girth or diameter of something round or thick in a non-flat way.
Used for thickness in the sense of girth or diameter, such as for ropes, tree trunks, arms, or columns. Derived from 太い (futoi, 'thick/fat').
このロープの太さは十分ですか？
Is the thickness of this rope sufficient?
彼の腕の太さに驚いた。
I was surprised at the thickness of his arms.
Describing how thick a liquid or semi-liquid substance is, like soup, paint, or fog.
Used for concentration or thickness of liquids, gases, or colors. Derived from 濃い (koi, 'thick/dense/strong').
スープの濃さを調節してください。
Please adjust the thickness of the soup.
霧の濃さで前が見えなかった。
I couldn't see ahead because of the thickness of the fog.
Specifically refers to a desirable, smooth thickness or viscosity, often in cooking (like a thickened sauce).
Describing non-physical thickness, such as of a book's content, atmosphere, or voice.
Can be used figuratively for depth or richness, like the thickness of a story or sound.
彼の声には厚みがある。
His voice has a certain thickness (richness).
Used for richness or intensity, such as of flavor, color, or atmosphere. Implies a dense, concentrated quality.
この絵の具の濃厚さが好きだ。
I like the thickness (richness) of this paint.
厚さ (atsusa) is for flat objects like paper or boards. 太さ (futosa) is for cylindrical or rope-like objects. 濃さ (kosa) is for liquids, gases, or colors. Using the wrong one can sound unnatural.
For human body parts, 'thickness' often translates to 太さ (futosa) for limbs, but for 'thick' as an adjective, 太い (futoi) is more common. Saying 厚い腕 (atsui ude) would mean a flat, board-like arm, which is incorrect.
This sauce has just the right thickness.