What Size Dildo Should You Choose?
A complete UK size guide — understanding length vs girth, beginner sizing, how to measure accurately and how to size up safely over time.
Shop DildosDildo sizing involves two distinct measurements: insertable length and girth. Both matter, but they matter in different ways and for different reasons. Understanding the difference — and knowing what sizes are appropriate for your experience level — is the foundation of a good buying decision.
Length vs Girth: What Is the Difference?
Insertable length is how much of the dildo actually enters the body. This is different from the overall length, which may include a handle or base that remains outside. When comparing dildos, always look at insertable length rather than total length.
Girth refers to the thickness of the toy, measured either as diameter (the width across the widest point) or circumference (the distance around the outside). Most product listings give diameter — circumference is approximately 3.14 times the diameter.
Most sex educators agree that girth has a greater impact on the sensation of fullness than length. The G-spot is located only a few centimetres inside the vagina, meaning extra length beyond moderate does not add proportionally to stimulation. Girth, on the other hand, directly determines how full the sensation feels throughout the entire experience.
Recommended Sizes by Experience Level
| Experience Level | Insertable Length | Diameter | Circumference |
|---|---|---|---|
| Complete beginner | 10–14cm (4–5.5") | 2.5–3.5cm (1–1.4") | 8–11cm (3.1–4.3") |
| Some experience | 12–16cm (4.7–6.3") | 3–4cm (1.2–1.6") | 9.5–12.5cm (3.7–4.9") |
| Experienced | 15–20cm (6–8") | 3.5–5cm (1.4–2") | 11–15.7cm (4.3–6.2") |
| Anal beginners | 10–14cm (4–5.5") | Under 3.5cm (1.4") | Under 11cm (4.3") |
Shop Dildos in Every Size at Ava Noir
Our full collection covers beginner to experienced sizes in body-safe silicone, glass and steel — all with clear dimensions listed. Discreet UK delivery available.
Shop NowHow to Measure for a Dildo
Before buying, it can help to use a ruler or soft tape measure to get a concrete sense of the dimensions you are considering. A ruler gives a clear visual of insertable length. To understand girth, wrap a tape measure around a similarly sized cylindrical object — a deodorant stick, a shampoo bottle, or even your fingers pressed together — to get a feel for circumference before committing to a purchase.
If you have previously used tampons or other insertable products comfortably, these give a useful baseline. A standard tampon applicator is approximately 1 to 1.2 centimetres in diameter. Two fingers side by side is approximately 3 to 3.5 centimetres. These reference points help translate abstract centimetre measurements into something physically meaningful.
How to Size Up Safely
When you are comfortable with your current toy and want to explore a larger size, increase gradually. The guideline most commonly recommended is to increase diameter by no more than 0.5 centimetres between toys. Always use plenty of lubricant when trying a new larger size for the first time. Allow your body more warm-up time than usual. If insertion feels forced or painful, the size increase is too large — step back and try again with a smaller increment.
For anal sizing, increase even more gradually and allow several sessions at each size before moving up. The anal sphincter needs time to adapt to new dimensions and rushing this process can cause discomfort or minor injury.