Durometer & Material Reference

Shore A hardness bands

Up to	Category	Feel	Typical examples	Approx. Shore D	Suited for	Trade-off
15A	Extra soft (gel)	squishes easily and feels gel-like	silicone gel insole, gummy candy, chest-expander gel	—	Vibration-isolation gel pads and cushioning inserts where almost all shock absorption matters and load-bearing does not.	Maximum grip and cushioning, essentially no load capacity — it spreads and bottoms out under any real weight.
30A	Soft rubber	pliable and easily bent between your fingers	rubber band, pencil eraser, soft silicone seal	—	Soft seals, light cushioning feet, and pliable trim where the part flexes constantly and never carries static weight.	Still grips and cushions well, but compresses and creeps under sustained load — not a structural foot.
45A	Medium-soft rubber	flexes readily but springs back	rubber stamp, door weatherstrip, swim goggles	8D	Door and window weatherstripping, soft cabinet bumpers, and light-duty feet under items that mostly just need quieting.	Good cushioning and gap-filling; noticeably less load capacity and shape retention than the medium band above it.
62A	Medium (typical rubber feet & bumpers)	firm but still visibly compresses under a thumb	car tire tread, rubber feet & bumpers, shoe sole	16D	General-purpose rubber feet, bumpers, and grip dots — the default choice when an item mostly needs to sit still and grip.	The balance point: firm enough to carry ordinary furniture loads, soft enough to grip and cushion a knock.
78A	Firm rubber	hard to dent by hand, gives only slightly	O-ring seal, hard shoe heel, trolley wheel	28D	Firm feet and bumpers for heavier static loads, and seals that need to hold their shape under sustained compression.	Carries more weight without spreading, but grips less and transmits more shock than the medium band.
90A	Hard rubber	barely yields to a fingernail	skateboard wheel, caster wheel, hard bumper	40D	Caster wheels, heavy-duty bumpers, and hard-wearing contact points that see repeated abrasion.	Excellent wear resistance and load capacity; grips poorly and feels harsh compared with softer rubber.
100A	Very hard rubber (semi-rigid)	feels almost like rigid plastic	hard hat brim, roller-skate wheel, shopping-cart wheel	58D	The hardest rubber before a part is better described as rigid plastic — semi-rigid wheels and structural bushings.	Essentially no cushioning left; chosen purely for wear resistance and dimensional stability.

Each row is a single representative reading run through the same durometer() classifier behind the calculator above — the category, feel, example materials, and Shore D equivalent are its live output, not a separately written description. A dash in the Shore D column means that reading falls outside the narrow band where the two scales genuinely overlap, so no equivalent is meaningful.

Recommended foot size by load

For a handful of common total loads split across four feet, here’s what our rubber foot and bumper size selectorrecommends at its own 300 kPa default working pressure, cross-checked against the furniture-foot load-capacity calculator to confirm each suggested standard size actually keeps the resulting pressure within that limit.

Total load	Load per foot	Required diameter	Suggested standard size	Utilization
5 kg	1.25 kg	7.2 mm	10 mm	52% (within limit)
10 kg	2.5 kg	10.2 mm	13 mm	61.6% (within limit)
20 kg	5 kg	14.4 mm	15 mm	92.5% (within limit)
40 kg	10 kg	20.4 mm	22 mm	86% (within limit)
80 kg	20 kg	28.9 mm	30 mm	92.5% (within limit)
150 kg	37.5 kg	39.5 mm	40 mm	97.5% (within limit)

These are planning figures, not certified load ratings — a sensible working pressure for sizing a pad, not a structural guarantee for any specific compound or floor. For a load heavier than the largest row here, see our worked example of sizing a foot from its load, which covers exactly the point where a standard round pad stops being the right answer.

Grip: a comparative illustration, not a spec

Coefficient of friction varies hugely with surface finish, contamination, and moisture, so these two rows from the anti-slip friction estimatorare shown purely to illustrate how much a change in coefficient matters for the same 10 kg item — not as a claim about what any specific rubber or floor will actually measure.

Coefficient	Max holding force	Equivalent to	Max stable incline
0.6	58.8 N	6 kg of push	31°
0.85	83.4 N	8.5 kg of push	40.4°

Frequently Asked Questions

Where do the numbers on this page come from?

Every category, feel description, example material, and Shore D equivalent on this page is computed by calling the same durometer() function our durometer hardness calculator uses, at a representative reading in each band. The foot-size figures likewise come from the same rubberFootSize() and furnitureFootLoad() functions behind our sizing calculators. None of it is a separately maintained table, so it can't drift out of sync with the calculators.

Why do some hardness values have no Shore D equivalent?

Shore A and Shore D only overlap in a narrow band at the hard end of Shore A, roughly 80-100, which is roughly 30-58 on Shore D. Below that overlap, a Shore D reading isn't meaningful for a soft material, so the calculator correctly returns no equivalent rather than inventing one.

Is the recommended foot size a guarantee for my specific item?

No. It's a sizing guide computed from a general 300 kPa working-pressure assumption, useful for comparing options and avoiding an obviously undersized pad. It isn't a certified structural rating for any specific rubber compound or floor material, and it shouldn't be relied on for anything genuinely safety-critical.

Why does the grip comparison use two coefficients instead of naming specific materials?

Coefficient of friction varies hugely with surface finish, contamination, and moisture, so attaching a single number to "rubber" or "tile" as if it were a fixed material property would be misleading. The two figures shown are illustrative endpoints for comparison, not a claim about what any specific pad or floor will measure.

Estimates only. Confirm hardness, load ratings, and friction against the manufacturer’s own data before relying on any of these figures for a safety-critical fitting.

Use it with

Durometer (Shore A/D) Hardness Guide— classify your own reading interactively instead of reading from the anchor values above.
Rubber Foot & Bumper Size Selector and Furniture-Foot Load-Capacity Calculator— run the same sizing math on your item’s exact weight and foot count.
How to Read a Durometer Number and Pick a Hardness for the Job — the guide version of the hardness table, worked through real product examples.
Sizing a Furniture Foot From the Load It Actually Carries — the guide version of the load table, including the case where standard sizes run out.