1. Standard Single Bed Sizes (Approximate).

The most common "standard single" is designed for one person, typically a child or an average-sized adult.
Width: 90 cm (approximately 35 inches).
Length: 190 cm to 200 cm (approximately 75 to 79 inches).
Common Regional Name: Twin (in the US/Canada, but see important note below).

2. Crucial Regional Variations.

This is where it gets important. The "single bed" you get depends heavily on where you are.
① United Kingdom, Ireland, Australia, New Zealand & much of Europe.
Standard Single: 90 cm x 190 cm (3'0" x 6'3"). This is the most common global standard.
Long Single: Often 90 cm x 200 cm (3'0" x 6'6") for taller individuals.
② United States & Canada.
The term "Twin" is used instead of "Single."
win Size: 97 cm x 191 cm (38" x 75"). Slightly wider and shorter than the UK single.
Twin XL (Extra Long): 97 cm x 203 cm (38" x 80"). Common in college dorms and for taller individuals.
③ Europe (Continental).
Sizes can vary by country. For example, in some parts of Europe, a single may be 100 cm x 200 cm.

3. Key Considerations When Choosing a Single Bed Size.

① Who is it for?
Child/Teen: A standard 90x190 cm is usually perfect.
Adult: Consider the sleeper's height. Anyone over 183 cm (6') may prefer a Long Single (200 cm) or Twin XL (203 cm).
Active Sleeper: A slightly wider option (like a US Twin or a 100 cm European single) might be more comfortable.
② Room Size: A general rule is to have at least 60 cm (24 inches) of walking space on each side and at the foot of the bed. Measure your room carefully.
③ Future-Proofing: If space allows, opting for a Small Double (aka "Three-Quarter" or "120 cm Wide") provides significantly more comfort for an adult and is a popular compromise.
④ Bedding & Cost: Ensure you can easily find sheets and duvet covers for the size you choose. Standard single bedding fits 90x190 cm beds. Non-standard sizes may have fewer, more expensive options.

Final Advice: Always measure your room, consider the sleeper's size and habits, and double-check the specific dimensions of the bed and mattress you are buying, not just the generic name.