The standard guzheng is about 1.63 m long with 21 strings, but minis run from one metre to 1.3 m, usually with 18 to 21 strings. Size is not a cosmetic matter: string length determines how complete the range is and how deep the bass goes, and body length determines how hard the instrument is to carry and store. Getting the size wrong is harder to fix than getting the price wrong.
Standard (about 1.63 m): the default. Full range, solid bass, and universal coverage of teaching, graded exams and performance. Method books and demonstrations are written for this size. If it fits in your home and you do not move it constantly, choose standard. Most purchasing decisions end here.
1.3 m mini: children and itinerant teachers. One size smaller, lighter and smaller in footprint, suited to children whose arms cannot yet span standard string distances, and to teachers who carry an instrument to lessons. Check that string positions and fingering match the standard, so the child does not face an action change later.
One-metre portable: travel and interest playing. Fits in luggage, suits business travel, impromptu playing in an office or tea room, and adult hobby practice. The cost is a more contained low register — a physical consequence of short strings, not a quality defect. Anyone playing seriously should still default to a standard instrument.
A simple rule of thumb: measure your space first — 1.7 m of length and room for a stand. If it fits, buy standard; if portability is genuinely required, choose a mini whose string layout matches the standard.
Unsure which size? Tell us the use case and the space available and we will give a specific recommendation, including trying both in person.