Cost & Quoting

Cost Per Seal: How to Quote Molded Gaskets and O-Rings

A practical cost model for elastomer seals and gaskets: what actually drives cost per unit and how to build a quote that holds up.

Cost per seal breaks into five buckets: material, press time, labor, scrap, and overhead with margin. For a mid-volume nitrile O-ring, expect roughly 35 to 50 percent material, 20 to 30 percent press and machine time, 10 to 15 percent direct labor, 5 to 12 percent scrap, and the balance in overhead and profit. A ring that quotes at 8 cents might carry 3.2 cents of compound, 2.0 cents of press time, 1.0 cent labor, 0.7 cent scrap, and 1.1 cents overhead. The Cost Per Seal calculator lets you load each bucket and see which one moves the total.

Material cost is charge weight times compound price, not part weight times price. This is the single most common quoting miss. If the finished ring weighs 1.66 g but the preform charge is 2.1 g to guarantee fill, you buy 2.1 g. At a nitrile price of 4.20 dollars per kg, that is 0.88 cents of compound per shot, but only 0.70 cents ends up in the part. The 0.18 cent difference is flash and sprue you still paid for. Specialty compounds swing this hard: FKM runs 22 to 40 dollars per kg, so the same ring in Viton costs 6 to 9 times the material.

Press time is priced by the cavity, not the part. Machine rate divided by cavitation output gives per-part press cost. A press at 85 dollars per hour running a 48-cavity tool at 650 good parts per hour costs 85 divided by 650, or 13.1 cents per part in raw machine time before you spread it across... wait, that is the gross. Correcting: 8,500 cents per hour divided by 650 parts equals 13.1 cents only if the press makes one part; with 48 cavities the rate is spread, so 85 dollars over 650 parts is 0.131 dollars, meaning press economics live or die on cavity count. Double the cavities and press cost per part roughly halves. Use Cure Press Capacity and Mold Cavitation Output to lock the denominator.

Flash and scrap are real money, not a rounding error. Flash scrap cost equals flash mass per shot times compound price times shots, plus the deflashing labor and any tumble or cryo-media cost. If each shot leaves 0.44 g of flash across 48 cavities, that is 21 g per cycle; at 691 cycles-worth per hour and 4.20 dollars per kg, flash compound alone is about 0.42 dollars per hour of pure waste, roughly 0.06 cents per part, before you add cryogenic deflash at 0.3 to 0.8 cents per part. The Flash Scrap Cost calculator separates recoverable material from the labor burn.

Reject rate multiplies everything upstream. A part that fails inspection has already absorbed full material, press, and labor cost, so a 6 percent scrap rate does not add 6 percent to cost, it divides your good-part cost by 0.94, a 6.4 percent uplift. At 3 percent scrap the uplift is 3.1 percent; at 12 percent it is 13.6 percent. Feed your Inspection Defect Rate into the quote as a divisor, not an adder. Chronic dimensional rejects usually trace back to a shrinkage or groove-fill error you can fix in the tool rather than eat forever in the price.

Overhead and tooling amortization decide whether a low-volume job is even worth quoting. A 48-cavity hardened tool at 60,000 dollars amortized over a 500,000-part program adds 12 cents per part; over 5 million parts it adds 1.2 cents. This is why the same ring quotes at 22 cents for a 100,000-piece order and 7 cents at 3 million pieces. Always state the tooling assumption and the volume band on the quote. Plant overhead, quality, and warehousing typically add 18 to 30 percent on top of direct cost before margin.

Build the quote bottom-up and pressure-test it against a top-down sanity check. Sum material, press, labor, scrap, and overhead per part, add 12 to 20 percent margin, then compare against comparable running jobs in dollars per kg of finished rubber shipped. Standard nitrile seals often land between 9 and 18 dollars per kg of product; if your bottom-up quote implies 40 dollars per kg on a commodity ring, you have a cavitation or scrap problem, not a pricing problem. The Cost Per Seal calculator runs both views side by side.

Three estimating errors sink otherwise good quotes. First, quoting on part weight instead of charge weight understates material 15 to 30 percent. Second, assuming nameplate cavitation instead of good-parts output ignores the 5 to 10 percent yield haircut and inflates capacity. Third, treating scrap as an additive percentage rather than a divisor understates cost by 0.5 to 2 points. Each is small alone, but stacked they can turn a 15 percent margin into a 2 percent loss on a multi-million-part contract. Lock charge weight, good-parts output, and scrap divisor before you sign.

Published 2026-07-01.