O-Ring Weight Calculator
Free O-Ring weight calculator. Enter an AS568 dash number or your own inside diameter and cross-section, pick a compound, and get weight per piece, per thousand, and pieces per pound.
Pick an AS568 dash number or type in your own size, choose a compound, and get the weight per piece, per thousand, and how many pieces make a pound. Handy for freight quotes, packaging, scrap value, and cycle counts. The Copy link to this size button puts your inputs in the address, so you can send someone a prefilled link instead of explaining the math over the phone.
Size and compound
Use the free-state inside diameter, not the groove or bore size.
Found on the cure sheet or material data sheet, usually between 1.00 and 2.20.
Give it a count and it will total the whole lot for you.
Weight
| Per 100 pieces | — |
|---|---|
| Per 1,000 pieces | — |
| Pieces per pound | — |
| Pieces per kilogram | — |
| Volume each | — |
| Total for your quantity | — |
Weights are estimates from the torus volume formula and typical specific gravity, figure plus or minus 3 to 5 percent on a real molded part. If the number has to be exact, ask us for the actual specific gravity on the compound you are buying.
How the math works
That is the standard torus volume. An O-Ring is a doughnut, so the ring is treated as a round cord of diameter CS bent into a circle whose centerline diameter is the ID plus one cross-section. Weight comes from multiplying that volume by the specific gravity of the rubber.
What to expect for accuracy
Figure the real part lands within about 3 to 5 percent of what you see here. Molded O-Rings carry dimensional tolerances, compounds vary batch to batch, and flash removal takes a little material off. Specific gravity also moves with durometer and filler package, so a 90 duro Buna-N runs heavier than a 70 duro. If the number has to be exact, weigh a sample or ask us for the actual specific gravity on the compound you are buying.
Typical specific gravity by compound
| Compound | Typical SG |
|---|---|
| Buna-N / Nitrile (NBR) 70 duro | 1.25 |
| Buna-N / Nitrile (NBR) 90 duro | 1.30 |
| Viton® / FKM 75 duro | 1.85 |
| Viton® GF / GFLT (FKM) | 1.90 |
| EPDM 70 duro | 1.15 |
| Silicone (VMQ) 70 duro | 1.15 |
| Fluorosilicone (FVMQ) | 1.40 |
| Neoprene (CR) | 1.42 |
| HNBR / Highly Saturated Nitrile | 1.28 |
| Aflas® (TFE/P) | 1.58 |
| Butyl (IIR) | 1.20 |
| Polyurethane (AU/EU) | 1.24 |
| SBR | 1.18 |
| Natural Rubber (NR) | 1.10 |
| Hypalon® (CSM) | 1.35 |
| PTFE, virgin | 2.16 |
| Kalrez® / FFKM | 2.00 |
Not sure which compound you need in the first place? Start with the materials guide, and find dimensions for any standard on the Master O-Ring Size Chart.
