ED ring size chart
To measure for an ED ring, wrap a soft tape around the base of the penis when fully erect and read the circumference. That number is your girth. For FirmTech rings, the only question is whether it is 5.5 inches (14 cm) or less; if it is, all three rings fit, because the strap adjusts.
Published by FirmTechLast updated November 2026
Measure erect girth at the base with a soft tape. Fixed rings are sold by inner diameter, so divide girth by 3.14 to convert. FirmTech rings skip that step: the TechRing, Performance Ring and MaxPR adjust to any erect girth up to 5.5 inches (14 cm), which FirmTech says covers 95% of men.
Step by step
Fit checker
Enter your erect girth at the base. You will see the matching diameter and whether it falls inside the FirmTech stated fit of up to 5.5 inches (14 cm).
Girth is the distance around; diameter is the distance across. Diameter equals girth divided by pi (about 3.14), so a 5.5 inch girth is about 1.75 inches across. Fixed rubber, silicone and metal rings, and the tension rings sold with vacuum pumps, are sized by diameter, so they need an exact match. Adjustable rings like FirmTech's only need you to stay within their maximum girth.
See the full erection ring size chartCommon mistakes
Measure erect. A ring sized to soft girth will be too tight once erect.
Measure at the base, where the ring actually sits.
Snug, not squeezing. A tight tape reads small and leads to a ring that is too tight.
FAQ
When erect, wrap a soft tape measure or a piece of string around the base of the penis. That number is your girth. FirmTech says that if it is 5.5 inches (14 cm) or less, its rings fit. To convert girth to the diameter used by solid rings, divide the girth by 3.1416.
Divide your circumference by pi, about 3.1416. A 5 inch girth equals about 1.59 inches, or roughly 40 mm, of diameter. Diameter matters most for solid, fixed-size rings. FirmTech adjustable rings are sized by girth instead, with a stated fit of up to 5.5 inches erect.
Yes. The size chart on this guide’s home page converts erect girth from 4 to 7 inches into centimeters and diameter, and marks which measurements fall inside the FirmTech stated fit of up to 5.5 inches. All three FirmTech rings share that range, so one chart covers the TechRing, Performance Ring and MaxPR.
FirmTech states its rings fit up to 5.5 inches (14 cm) of erect girth, so a larger measurement falls outside the published range. Contact FirmTech through getfirmtech.com/contact before buying to ask about fit. FirmTech also offers a 30-day money-back guarantee if a ring does not meet your expectations.
Yes. FirmTech says its rings are designed to go on while you are soft, so you can put one on discreetly ahead of time. You hold the loop open, place the testicles through one loop, set the other loop around the base of the penis, then adjust the tension for comfort.
With FirmTech rings, you do not need to pick a size. FirmTech says one size fits 95% of men, up to 5.5 inches (14 cm) of erect girth, and the hook-and-loop strap adjusts to your exact size. If your erect girth is above 5.5 inches, contact FirmTech before ordering to ask about fit.
Keep reading
Ask FirmTech before you buy. Questions about sizing, the app or HSA/FSA go straight to the customer service team by email.
Published by FirmTech
