What size is a China 33 x 48 mm?

A China 33 x 48 mm is 33 x 48 mm (390 x 567 pixels at 300 dpi).

How big should the head be in a China 33 x 48 mm?

The head should measure 28 to 33 mm from chin to crown, on a #FFFFFF background.

China 33 x 48 mm

China 33 x 48 mm: 33 x 48 mm, head height 28-33 mm, #FFFFFF background. Make one free, no signup.

Photo size	33 x 48 mm
At 300 dpi	390 x 567 px
Head height	28-33 mm (chin to crown)
Background	#FFFFFF
Resolution	300 dpi

Not confirmed against a primary source. These figures follow the international (ICAO) standard rather than a published China requirement. Check them with the issuing authority before you apply.

Notes

Widely published NIA visa/passport size; not re-checked against a primary source.