How to read measurements on an 18+ product page: length, insertable length, and diameter
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by Verpakkingdeals.nl
5 min reading time
Total length, insertable length, diameter, and circumference all mean something different. This buying guide explains how to read and convert 18+ product sizes.
On a product page, it says "25.5 cm". The description mentions "insertable length 12 cm". And the title of another item suddenly says "6.7 inch". These three numbers all refer to the same type of product but mean something different. If you only pay attention to the largest number, you'll regularly order something that turns out to be very different in practice than expected. This guide explains what measurements you'll encounter with 18+ items, how to convert them, and what to consider before clicking "order".
Total Length Is Not Usable Length
The measurement most often found in a product title is the total length: from the bottom of the base to the top. This often includes a part not intended for insertion — a wide base, a suction cup, a handle, or a battery compartment. The usable or insertable length is therefore always shorter, sometimes significantly.
Consider the difference between the Rocket John Realistic Dildo 16.5 cm (€18.99) and the Rocket John Realistic Dildo 25.5 cm Black (€19.99). On paper, that's a nine-centimeter difference, but both have a part of the base that is not insertable. If the insertable length is not mentioned, don't guess: ask. A rough rule of thumb is that for models with a wide base, you should subtract a few centimeters from the total length, but the exact amount varies per model.
Diameter and Circumference: One Number, Two Meanings
For thickness, you'll encounter two measurements. The diameter (sometimes abbreviated as "dia" or "Ø") is the cross-section: the distance straight through the thickest point. The circumference is the distance around it. They differ by approximately a factor of three: circumference ≈ diameter × 3.14.
That explains why people make mistakes. A product with "3 cm" in the title, such as the Double Dildo Rocket Dong Black 20.4 x 3 cm (€14.99), therefore has a circumference of roughly 9.4 cm. If you see "9 cm" somewhere, check if that's the circumference and not the diameter — otherwise, you'll order something three times thicker than you thought. And remember: for thickness, every millimeter counts. Going from 3 to 4 cm diameter sounds like a small difference, but it's a third more in circumference.
Inches, mm, and Other Abbreviations
Many 18+ items come from international manufacturers, so you'll see inches. The conversion is simple: 1 inch = 2.54 cm. A product labeled as 6.7 inches, such as the Anal Dildo Plug Black 17 cm (€9.95), is therefore approximately 17 cm. Good to know: manufacturers round numbers. 6.7 inches is exactly 17.018 cm, and that becomes 17 cm on the Dutch page. A difference of a few millimeters between two sources is usually rounding, not an error.
Other abbreviations you'll encounter: "L" or "length" for total length, "insert length" or "insertable" for the usable part, "W" or "width" for the width, and "head" for the diameter of the tip. The latter is relevant because the tip on some models is wider than the rest — then it's not the average, but that thickest point that determines the measurement.
Material Changes What a Measurement Means
Two products with the same dimensions can feel completely different because the material varies in hardness and flexibility. Hard material doesn't give way, so the stated measurement is truly the measurement. With softer materials, the product flexes, and the same diameter feels less large.
Also, pay attention to the base. A wide, flat base or a suction cup is not only functional but also a safety feature for anal use: products without a flared base are not suitable for it. This is not always explicitly stated on the page, but you can see it in the photo.
How to Make a Size Concrete Before Ordering
Numbers on a screen say little. Make them tangible with these three steps:
Measure it against something familiar. Place a ruler next to an object at home and see what 17 cm or 20 cm actually is. A standard pen is about 14 cm, an A5 sheet is 21 cm long.
Calculate the circumference. Multiply the diameter by 3.14 and measure that circumference with a piece of string or a tape measure. That's more informative than the number itself.
Compare with what you already have. If you already have something at home, measure it and use it as a reference point. That's the most reliable comparison there is.
And when in doubt: choose the smaller size. A product that is on the modest side will be used. A product that turns out too large disappears into a drawer — and 18+ items usually cannot be returned once the seal is broken due to hygiene reasons. So, before ordering, check the return conditions on the product page.
What You Need With It
Regardless of the size, lubricant is needed, and more than you think. Water-based is the safest standard choice because it works with almost all materials; silicone lubricant is usually discouraged by manufacturers on silicone products, as it can damage the surface. For glass, it makes no difference in terms of material.
If you want to compare sizes, look in Dildos, in Anal Sex Toys for models with a flared base, and in Lubricant for what goes with them. Is an insertable length or diameter not mentioned, and you want to know it before ordering? Email the product link to info@verpakkingdeals.nl — we will measure it or ask the supplier. All orders are shipped in neutral packaging.
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