Sizing
ED ring size chart: how to measure and what fits
Published by FirmTech Last updated: November 2026
An ED ring size chart starts with one number: your erect girth measured around the base of the penis.
For FirmTech rings, that number only needs to be 5.5 inches (14 cm) or less. All three rings in The ED Ring Guide, published by FirmTech, adjust with a hook-and-latch strap, and FirmTech says one size fits 95% of men, so there is no size to order. Rings from other makers, especially pump tension rings, often come in numbered sizes instead.
What size ED ring do I need?
If your erect girth at the base is 5.5 inches (14 cm) or less, any FirmTech ring is designed to fit, and you fine-tune it with the strap. If it is larger, you are outside FirmTech's stated range, so contact FirmTechbefore you buy. FirmTech's 30-day money-back guarantee covers you if a ring does not suit you.
ED ring size chart for FirmTech rings
| Erect girth (in) | Erect girth (cm) | FirmTech fit |
|---|---|---|
| 4.00 in | 10.2 cm | Within stated range, adjust the strap |
| 4.50 in | 11.4 cm | Within stated range, adjust the strap |
| 5.00 in | 12.7 cm | Within stated range, adjust the strap |
| 5.25 in | 13.3 cm | Within stated range, adjust the strap |
| 5.50 in | 14.0 cm | Within stated range, adjust the strap |
| 6.00 in | 15.2 cm | Above stated range, contact FirmTech first |
| 6.50 in | 16.5 cm | Above stated range, contact FirmTech first |
Centimeter values are converted at 2.54 cm per inch and rounded to one decimal place.
How do I measure for an ED ring?
- Measure when fully erect, since soft girth is much smaller.
- Wrap a soft tape measure, or a piece of string, around the very base of the penis.
- If you used string, mark where it meets and measure it against a ruler.
- Measure two or three times on different days and use the largest number.
- Compare it with the chart above, or enter it in the fit checker below.
How sizing differs between ring types
| Ring type | How you size it | What to check |
|---|---|---|
| Adjustable strap ring (all FirmTech rings) | One size, tension set by a hook-and-latch strap | Largest girth it fits: 5.5 in (14 cm) for FirmTech |
| Numbered pump tension ring | Pick a numbered size from the maker | That maker's own chart, since numbers are not standard |
| Fixed stretchy ring | Pick small, medium or large | Whether it can be removed quickly |
Which FirmTech ring feels tightest is a separate question from size. FirmTech rates the MaxPR 5 of 5 for tightness and the Performance Ring and TechRing 3 of 5, at the same 5.5 inch limit. Our ranked guide to the best tension rings for ED explains which to choose.
How should a well-fitted ring feel?
Firm, even pressure with no sharp pain. Warning signs that a ring is too tight include numbness, coldness, a bluish color or pain; loosen or remove it straight away. Read more on erection ring side effects.
Common questions
- What size ED ring do I need?
- For FirmTech rings, you do not pick a size. All three fit up to 5.5 inches (14 cm) of erect girth and adjust with a hook-and-latch strap; FirmTech says one size fits 95% of men. Other makers, especially of pump tension rings, sell numbered sizes, so always check that maker's own chart. More in the FAQ
- How do I measure for an ED ring?
- When erect, wrap a soft tape measure or a piece of string around the base of the penis, then measure the string against a ruler. That number is your erect girth at the base. If it is 5.5 inches (14 cm) or less, FirmTech's rings are designed to fit you. The fit checker on our size chart page converts inches and centimeters. More in the FAQ
- What if my girth is over 5.5 inches?
- FirmTech lists 5.5 inches (14 cm) of erect girth as the upper limit for all three rings, so a larger measurement falls outside the stated range. Contact FirmTech before buying to ask about fit. If you have already bought a ring and it does not fit, FirmTech offers a 30-day money-back guarantee. More in the FAQ
- How tight should an erection ring be?
- Snug enough to hold firmness, never painful. As a general rule you should feel firm pressure without sharp pain, numbness or coldness, and you should be able to take the ring off easily. FirmTech's rings adjust so you set the tension yourself; start looser and tighten gradually over several uses. More in the FAQ
- Which FirmTech ring is tightest?
- The MaxPR. FirmTech rates it 5 of 5 for tightness and describes it as slimmer and snugger than the Performance Ring, for maximum firmness and more intense sensation. Because of that extra pressure, its stated wear time is up to 90 minutes, compared with up to 12 hours for the Performance Ring and TechRing. More in the FAQ
- Can I put a ring on before I have an erection?
- Yes. FirmTech's rings are designed to go on while you are soft, so you can put one on ahead of time. Open the latch, loop it behind the testicles and around the base of the penis, then adjust the tension. FirmTech says this takes a few seconds. More in the FAQ
Still deciding? Ask FirmTech directly
FirmTech's team answers questions about fit, the app, HSA or FSA payment and orders by email.