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Reference · Pad Printing
Shore Hardness Scale Comparison Chart
Convert between Shore A, B, C, D, O and OO — and find the pad durometer that matches the part you are printing.
Download the chart (PDF)
The original one-page chart, unchanged.
Shore hardness — durometer — measures how far a standard indenter sinks into a material under a standard force. It is the number that tells you whether a silicone is soft enough to wrap a curved part or hard enough to hold fine detail. Higher number, harder material. The test method is ASTM D2240.
There is no single Shore scale. Each one uses a different indenter shape and spring force, so each covers a different band of stiffness. A material soft enough to read sensibly on Shore OO would barely register on Shore D, and vice versa. That is why a conversion chart exists at all.
Shore hardness conversion chart
| Shore A | Shore B | Shore C | Shore D | Shore O | Shore OO |
|---|---|---|---|---|---|
| 100 | 85 | 77 | 58 | ||
| 95 | 81 | 70 | 46 | ||
| 90 | 76 | 59 | 39 | ||
| 85 | 71 | 52 | 33 | ||
| 80 | 66 | 47 | 29 | 84 | 98 |
| 75 | 62 | 42 | 25 | 79 | 97 |
| 70 | 56 | 37 | 22 | 75 | 95 |
| 65 | 51 | 32 | 19 | 72 | 94 |
| 60 | 47 | 28 | 16 | 69 | 93 |
| 55 | 42 | 24 | 14 | 65 | 91 |
| 50 | 37 | 20 | 12 | 61 | 90 |
| 45 | 32 | 17 | 10 | 57 | 88 |
| 40 | 27 | 14 | 8 | 53 | 86 |
| 35 | 22 | 12 | 7 | 48 | 83 |
| 30 | 17 | 9 | 6 | 42 | 80 |
| 25 | 12 | 35 | 76 | ||
| 20 | 6 | 28 | 70 | ||
| 15 | 21 | 62 | |||
| 10 | 14 | 55 | |||
| 5 | 8 | 45 |
Treat these as approximate. The scales are not related by a formula — they are different tests. Two materials that read the same on Shore A can read differently on Shore D depending on how the polymer behaves under load. Use the chart to find the right range, then measure on the scale you actually intend to specify.
Which scale applies to what
- Shore OO — the softest. Foams, gels, sponge rubber.
- Shore O — soft rubbers and very soft elastomers.
- Shore A — the working scale for flexible rubbers and silicones. Pad printing pads are specified on Shore A.
- Shore B and C — intermediate scales, used where a material sits above the useful range of A but below D.
- Shore D — hard rubbers and rigid plastics. This is the scale that matters when the part you are decorating is the thing being measured.
For accurate readings, the specimen needs to be at least 6 mm thick, flat, and read at a consistent dwell time. Thin or curved samples read harder than they are, because the anvil beneath them carries some of the load.
Pad printing pad durometers
EPS silicone pads are graded by letter, each covering a five-point band on Shore A. The letters are the legacy Pad Print Machinery of Vermont coding and are still used across the current range.
| Grade | Shore A | Stock color |
|---|---|---|
| — | 75 – 80 | |
| M | 70 – 75 | |
| L | 65 – 70 | Standard red |
| K | 60 – 65 | |
| J | 55 – 60 | Standard blue |
| I | 50 – 55 | |
| H | 45 – 50 | |
| G | 40 – 45 | |
| F | 35 – 40 | |
| E | 30 – 35 | |
| D | 25 – 30 | |
| C | 20 – 25 | |
| B | 15 – 20 | |
| A | 10 – 15 |
Choosing a pad durometer
The rule is short: soft for irregular surfaces, hard for fine detail.
A softer pad deforms more, so it wraps further around a curve, drops further into a recess, and tolerates variation between parts. What it gives up is precision — a pad that is deforming a lot is also stretching the image as it lays it down. A harder pad holds the image geometry far better and releases ink more cleanly, but it needs a surface close enough to flat that it can make contact everywhere at once.
Most production sits in the middle, which is why L (65–70 A, standard red) and J (55–60 A, standard blue) are the two stock grades. Reach for the softer end when the part fights you, the harder end when the artwork is fine and the surface cooperates.
Durometer is only one of five things needed to specify a pad. The others are the machine model the pad runs on, the part geometry, the image area and aspect ratio, and the silicone formulation — standard, solvent-resistant, or food-grade. Full ordering detail is on the pads page, and stock pads ship the same day.
Why it changes the print
Pad hardness is one of the three variables that decide whether ink ends up where you want it — the other two being the plate etch depth and the ink matched to the substrate. A pad that is too hard for the geometry skips contact and drops out detail at the edges of the image. A pad that is too soft smears the image as it rolls into the part, and can pick up ink it should have left behind. Both look like ink problems and neither is one.
Related
What you probably came here to specify.
Common questions about Shore hardness
What does Shore hardness measure?
How far a standardised indenter sinks into a material under a standardised force, measured per ASTM D2240. The scale runs 0 to 100 and a higher number means a harder material. It is a measure of indentation resistance specifically — not of strength, tear resistance, or how long the material will last.
What is the difference between Shore A and Shore D?
They use different indenters and spring forces, so they cover different bands. Shore A is for flexible rubbers and silicones; Shore D is for hard rubbers and rigid plastics. The overlap is narrow — above roughly 90 Shore A, readings compress and Shore D becomes the more useful scale. Printing pads are always specified on Shore A.
Can you convert Shore A to Shore D exactly?
No. They are separate tests, not two units of the same measurement, so no formula converts between them reliably. A comparison chart like the one above gets you to the right range, which is usually all you need to pick a material. If a specification has to be met, measure on the scale the specification names.
What durometer are pad printing pads?
EPS pads run from about 10 to 80 Shore A, graded by letter in five-point bands. The two stock grades are L at 65–70 A (standard red) and J at 55–60 A (standard blue). Softer and harder grades are available, and custom pads are molded to order on roughly a seven business day cure cycle.
Which pad durometer should I use?
Soft for irregular surfaces, hard for fine detail. A softer pad wraps further around curves and into recesses and tolerates part-to-part variation; a harder pad holds image geometry better and releases ink more cleanly, but needs a surface close to flat. Most production runs on the middle grades. If the part is unusual, send it to us and the lab will tell you which pad it wants rather than guessing from a chart.
What do the letters on an EPS pad mean?
Each letter is a five-point band on Shore A — A is the softest at 10–15, M the hardest at 70–75. The coding dates from Pad Print Machinery of Vermont, the company EPS grew out of, and is still used across the current pad range so legacy part numbers keep working.
Not sure which pad your part needs?
Send us the part. Our applications lab will tell you the shape, durometer and silicone formulation it actually wants — and print a sample on it before you buy anything.