Strap On Sizing Guide

by Kate Miller on Jan 22 2026

Strap ons come in a range of sizes from under 5 inches and can range up to between 9 and 10 inches. Circumference sizes range from beginners at around 4 inches, up to larger sizes of between 5.5 inches and 7 inches (or above). So knowing the size of the strap-on to get is critical for safe, comfortable and pleasurable use. Thus, we preprared the following strap-on sizing guide where we disucss how to measure yourself and your partner for a most fitting strap-on toy!

How to Measure for a Strap-On?

To measure a vagina, you will need a vibrator (if possible), or an alternative object which is long, clean and has a smooth surface. To begin, either you or your partner lay on their back with legs spread. The vagina needs stimulating at this point, as it elongates when it is aroused. Once aroused, you can start sliding the vibrator or phallic object into the vagina. When you reach the max comfortable depth, mark this on the vibrator/phallic object. This is the strap on length (for the dildo or vibrator) which the vagina can safely handle.

To measure circumference or girth, you can use your fingers and slide one at a time until you reach the limit. Then, wrap the tape measure around the fingers and you;ll get the circumference of the strap-on the vagina can comfortably take..

Sex Toy Measurements

Generally speaking there are four vital measurements for any sex toy you need to know:

  • Length: The full length of the toy from the two farthest points, which we refer to as total lenght.
  • Insertable Length: The length of the toy that can be safely inserted.
  • Width (or diameter): The distance between the two sides of the toy.
  • Girth (or circumference): The circumference of the toy which is relevant to insertable toys.

Sizing for Hollow Strap-Ons

A hollow strap-on is mostly worn by men who have a smaller penis, so for these, measure the length f the penis when it is fully aroused (if possible). It is the measurement that ensures the penis will fit in the hollow dildo canal.This is to make sure they can fit their penis inside the hollow canal.

Make sure you measure the circumference and calculate the diameter, as most product descriptions share the diameter of the hollow dildo strap-on. It is a simple math - divide the circumference by 3.14 and you'll get the diameter, and you'll know the size to look for.

Shop Hollow Strap-Ons

Shop Hollow Strap-Ons

Hollow Silicone Dildo Strap On
Hollow Silicone Dildo Strap On

Hollow Silicone Dildo Strap On

(3)

$73.95 $51.95
Color
Master Series Inflatable Hollow Strap On
Master Series Inflatable Hollow Strap On

Master Series Inflatable Hollow Strap On

(7)

$88.95 $69.95
Fetish Fantasy Series 7 Inch Hollow Strap-On With Balls
Fetish Fantasy Series 7 Inch Hollow Strap-On With Balls

Fetish Fantasy Series 7 Inch Hollow Strap-On With Balls

(3)

$76.24 $60.99
Fetish Fantasy Series 9 Inch Hollow Strap-On With Balls
Fetish Fantasy Series 9 Inch Hollow Strap-On With Balls

Fetish Fantasy Series 9 Inch Hollow Strap-On With Balls

(3)

$82.49 $65.99
View All Hollow Strap-Ons

Sizing for Vibrating Strap-Ons

You need to measure the length and circumference of the vibrating strap-on. If you get a simpler vibrating strap-on with a dildo and an harness, then only measure the safe size the receiver can manage. But if you are looking to buy a strapless strap-on, then you should also know the size the wearer can manage.

To measure for a strapless strap-on, you need to measure the size the vagina can safely take, as the strapless strap-on is worn in the vagina and held in place by the Kegel muscles. If you have previous experience with egg vibes, these can be a good starting point. However, if you don't have a previous reference, then use deduction to find a model that will be comfortable. Even better, you can get an inflatable strapless strap-on for a perfect fit.

Shop Vibrating Strap-Ons

Shop Vibrating Strap-Ons

Double Delight Dual Insertion Vibrating Rabbit Cock Ring - Purple
Double Delight Dual Insertion Vibrating Rabbit Cock Ring - Purple

Double Delight Dual Insertion Vibrating Rabbit Cock Ring - Purple

(3)

$81.95 $56.95
Shots Ouch Vibrating Silicone Strapless Strap-on
Shots Ouch Vibrating Silicone Strapless Strap-on

Shots Ouch Vibrating Silicone Strapless Strap-on

(9)

$54.95
Color
Strap U Slim Ribbed Vibrating Strapless Stap On
Strap U Slim Ribbed Vibrating Strapless Stap On

Strap U Slim Ribbed Vibrating Strapless Stap On

(9)

$135.00 $92.95
Strap-On-Me Vibrating Strapless Strap On - M
Strap-On-Me Vibrating Strapless Strap On - M

Strap-On-Me Vibrating Strapless Strap On - M

(18)

$187.49 $149.99
View All Vibrating Strap-Ons

Sizing for Strap-On Compatible Dildos

Strap-on or harness compatible dildos are designed to give a unique feel to the receiver. They come in varying ranges, so you can get a small, medium, and even large strap-on compatible dildos. To measure the insertable length, you can us ethe method we described above: measure the length the vagina can safely take when it is fully aroused. Do this with a dildo, a vibrator or another phallic object and you'll get the length of the dildo. While you are at it, measure the circumference and calculate the diameter, and you'll get a good idea of the size of strap-on compatible dildo to get.

You can find insertable lengths of strap-on compatible dildos at around 5 to 6 inches and then larger varieties of between 7 to 8 inches. Please note that to fit the dildo in the strap-on, you need to take into account the O-ring and base, as once fitted in the harness, the insertable lenght gets shorter. In any case, our product descriptions tend to share the insertable length for most strap-on compatible dildos, so we have you covered.

Shop Strap-On Compatible Dildos

Shop Dildos for Strap-Ons

Fleshstixxx 7 Inch Dual Density Dildo
Fleshstixxx 7 Inch Dual Density Dildo

Fleshstixxx 7 Inch Dual Density Dildo

(21)

$56.94 From $45.55
Color
King Cock 8 Inch Dildo
King Cock 8 Inch Dildo

King Cock 8 Inch Dildo

(3)

$35.99
Color
Strap-On-Me Small Squirting Dildo Cum - Vanilla
Strap-On-Me Small Squirting Dildo Cum - Vanilla

Strap-On-Me Small Squirting Dildo Cum - Vanilla

(0)

$114.99 $91.99
Dr. Skin Plus 5 Inch Posable Dildo with Suction Cup
Dr. Skin Plus 5 Inch Posable Dildo with Suction Cup

Dr. Skin Plus 5 Inch Posable Dildo with Suction Cup

(0)

$26.95 $21.43
View All Dildos for Strap-Ons

Sizing for Strap-On Harness

To measure for a strap-on harness is much easier than measuring for the accompanying toy. Becasue most strap-on harnessses are adjustable, you can look at the general product description where we share the range of adjustability, so you will know your chosen model will be the right ft.

Measure you waist for the main waist size; then measure around your thighs where the harness will fit. For this, we recommend you use a flexible tape measure that will allow you to wrap it around your thighs and butt, measuring the exact size you need. Also, note that most adjustable strap-on harnesses have a give of about 5-10 inches, so you can safely get a model that appeals to you visually and you can expect it will fit you nicely.

If you are going after a strap-on underwear model, then you need to be more careful, as these are not adjustable. Our product descriptions list the sizes for each strap-on underwear model, which are comparable to the US dress sizes, so you can find the one that is closest to your size. We also have a plus-size strap-on harnesses and underwear category for those ladies with broader hips.

Shop Strap-On Harnesses

Shop Strap-On Harnesses

Strap U Mod Active Style Harness with O Ring- M/L
Strap U Mod Active Style Harness with O Ring- M/L

Strap U Mod Active Style Harness with O Ring- M/L

(4)

$45.95 From $36.95
Her Royal Harness Boxer Brief
Her Royal Harness Boxer Brief

Her Royal Harness Boxer Brief

(3)

$49.95 From $40.95
Strap-On-Me Diva Lingerie Harness
Strap On Me Lacy Diva Harness

Strap-On-Me Diva Lingerie Harness

(7)

$66.25 From $48.95
Strap On Me Rebel Harness
Strap On Me Rebel Harness

Strap On Me Rebel Harness

(9)

$45.00 From $33.95
View All Strap-On Harnesses

Learn More With Our Other Strap-On Guides:

How to Use a Strap-On?
How to Chose a Hollow Strap-On?
How to Use Hollow Strap-On?
How to Choose a Strap-On Harness?
How to Choose a Strapless Strap-On?
How to Choose a Vibrating Strap-On?

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