Size the pad, then size the thickness
Enter the load your outrigger actually carries and the ground condition to get the recommended HDPE pad thickness (10–90 mm, 25–280 T) — then use the quantity side to check pad area and container loading.
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RUIYANG manufactures HDPE, UHMWPE and FRAS composite crane pads, outrigger pads and ground protection mats for construction, oilfield, mining and civil projects worldwide. Tell us your reaction loads and ground — we reply with specifications and factory-direct pricing.
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Sizing a crane mat is a three-step calculation: (1) find the worst-case outrigger reaction — the load on the single most heavily loaded leg, often 50% of crane gross weight; (2) divide it by the pad area to get ground bearing pressure; (3) choose the RUIYANG thickness grade (10 mm 25–33 T through 70–90 mm 190–280 T) that carries that load with at least a 10% margin, then step up for stiffness. For a 60 t mobile crane that is 30 t per outrigger, about 99 kPa under a 1220 × 2440 mm pad, and a practical specification of 40–50 mm.
"What size crane mat do I need?" is really three questions stacked on top of each other, and most sizing errors happen because they get collapsed into one. The crane's tonnage is not the load on the mat. The mat's load rating is not its stiffness. And a pad that passes the bearing-pressure check can still dish under an outrigger float. Here is the sequence in the order it should be done.
Step 1: find the worst-case outrigger reaction
Load distribution across outriggers depends on boom configuration, slew angle, radius and counterweight. The design case is always the single most heavily loaded leg, and for a mobile crane that is routinely half the gross weight or more. A transparent first estimate is 50% of crane gross weight on one outrigger, then refine it with the manufacturer's load chart.
| Crane class | Gross weight | Worst-case outrigger reaction (at 50%) | Practical pad thickness |
|---|---|---|---|
| Mobile crane up to 25 t | 25 t | 12.5 t | 15–25 mm |
| 40 t truck crane | 40 t | 20 t | 25–40 mm |
| 60 t mobile crane | 60 t | 30 t | 40–50 mm |
| 100 t all-terrain crane | 100 t | 50 t | 50–70/90 mm |
| 200 t+ crane | 200 t+ | 100 t+ | 70–90 mm plus cribbing |
Treat the reaction column as an illustrative starting point for sizing a pad, not as a substitute for the load chart. What matters for the rest of this page is that a 60 t crane puts roughly 30 t — not 60 t — on the outrigger you are buying a pad for.
Step 2: pad area decides ground bearing pressure
Bearing pressure = outrigger reaction ÷ contact area. This is where pad size does its work, and the numbers move fast:
| Contact area | Equivalent pad | Pressure at 30 t | Pressure in kPa | Ground it suits |
|---|---|---|---|---|
| 0.25 m² | Bare 0.5 × 0.5 m float | 120.0 t/m² | 1,177 kPa | Concrete slab only |
| 0.50 m² | 0.7 × 0.7 m float | 60.0 t/m² | 589 kPa | Very stiff, engineered fill |
| 1.00 m² | 1.0 × 1.0 m pad | 30.0 t/m² | 294 kPa | Dense granular ground |
| 1.49 m² | 1220 × 1220 mm | 20.2 t/m² | 198 kPa | Firm ground |
| 2.98 m² | One 1220 × 2440 mm mat | 10.1 t/m² | 99 kPa | Firm to sandy ground |
| 5.95 m² | Two 1220 × 2440 mm mats | 5.1 t/m² | 49 kPa | Soft, wet or made ground |
Typical allowable bearing pressures for reference: dense sand and gravel in the 200–400 kPa range, stiff clay around 150–300 kPa, loose sand 100–150 kPa, and soft clay, silt or made ground below 100 kPa. Size the pad so the pressure at the outrigger lands inside the band for your ground — most crane pad enquiries resolve at one mat per outrigger on firm ground and two on soft ground.
Sizing a pad? Start here
These open the calculator with the outrigger reaction as the weight and a single-pad footprint. Change the ground condition to watch the required thickness move.
Step 3: thickness — load first, then stiffness
Feed the outrigger reaction into the calculator and it returns the thinnest grade whose verified rating covers it, plus the safety margin. Three examples, in increasing order of load:
- 30 t reaction on firm ground returns 10 mm (25–33 T) at a 9.1% margin — inside the rating, but with almost nothing spare, so 15 mm is the load-safe minimum.
- 100 t reaction on sand returns a required load of 130 t and lands in the 50 mm grade (130–155 T) at a 16.1% margin. It fits — but note how far it jumps: 40 mm tops out at 125 T, so one extra tonne of reaction would have pushed the specification a whole grade deeper.
- 180 t on firm ground returns 60 mm (160–185 T) at a 2.7% margin. Inside the rating on paper, with essentially no headroom for a soft spot, so the sensible answer is 70–90 mm.
That is the load answer. The pad answer is thicker, and the reason is bending. An outrigger float contacts only the middle of a pad, so the panel has to carry the load to its own edges without dishing — a stiffness requirement the tonnage table cannot express. In practice, outrigger pads start at 25 mm and settle at 40–50 mm for a 60 t crane and 70–90 mm for the heaviest machines. RUIYANG's 70–90 mm grade is rated 190–280 T and is specified for exactly this.
Pads, cribbing and platforms — which do you need?
| Component | Job | Typical RUIYANG grade |
|---|---|---|
| Outrigger pad | Spread one concentrated point load under a float or jack | 25–70/90 mm |
| Cribbing plate | Short, stiff plates stacked where a single pad lacks area or height | 40–70/90 mm |
| Crane mat / access mat | Running surface and working platform under the whole machine | 20–50 mm |
| Crane pad farm | Full platform of locked mats under all four outriggers | 30–50 mm |
Stacking deserves a caution. Two thin pads stacked do not equal one deep pad: the interface can slide, the top pad can rock, and the load path becomes unpredictable. If you need height, use purpose-made cribbing rather than loose mats — see cribbing plates for outriggers. If you need area, add mats side by side and lock them with 4-way connectors so the platform behaves as one surface.
What HDPE gives you under an outrigger
- A solid sealed core. Load spreads through the panel rather than relying on mass — which is why 70–90 mm carries 190–280 T.
- A flat, stable contact face. No timber that compresses unevenly, no steel that rusts and becomes slick.
- 0% water absorption. A pad left in the rain performs exactly as it did on delivery.
- Dual-side anti-slip texture. Keeps the float from creeping on the pad, and the pad from creeping on the ground.
- Handling you can plan for. A 20 mm pad weighs 59.5 kg; the equivalent steel plate is roughly 467 kg. See the crane mat weight calculator.
For the wider picture on crane support, see crane mats, crane stabilizer pads and crane outrigger pads and rig mats.
Frequently Asked Questions
How is crane mat load distributed?
A crane does not put its gross weight on one mat. It transfers load through the outrigger or track that is carrying the moment, so the design case is the worst-case outrigger reaction — commonly half or more of the crane's gross weight. That reaction is then divided by the pad area to give ground bearing pressure, and the mat thickness is chosen so the pad can spread that pressure without dishing.
How do I size a crane mat for an outrigger?
Three steps. First find the worst-case outrigger reaction — for a 60 t mobile crane, assuming 50% of gross weight gives 30 t. Second choose a pad area that brings the bearing pressure under the allowable for the soil: a 1220 × 2440 mm pad spreads 30 t over 2.9768 m², or about 99 kPa. Third pick the thickness that carries that load with margin, then step up for stiffness.
What thickness crane pad do I need for a 60 ton crane?
A 30 t outrigger reaction is inside the 10 mm grade (25–33 T) but with only 9.1% margin, so 15 mm is the load-safe minimum. For an outrigger pad, stiffness matters as well as load: the float contacts only the middle of the pad, so pads are practically specified from 25 mm upward and typically at 40–50 mm for a 60 t crane.
What is the difference between a crane mat, an outrigger pad and cribbing?
All three spread load, at different scales. A crane mat or access mat forms the running surface or working platform. An outrigger pad sits directly under the float or jack to spread a concentrated point load. Cribbing is a stack of short, stiff plates used when a single pad cannot provide enough area or height.
Can I use HDPE mats as crane outrigger pads?
Yes, up to the rating of the grade. RUIYANG HDPE crane pads run from 10 mm (25–33 T) to 70–90 mm (190–280 T) in 1220 × 2440 mm panels, with a solid sealed core that resists dishing and a dual-side anti-slip texture that keeps the float from sliding. They are also 0% water absorbing, so a pad left out in rain performs identically.
How many mats should I stack under an outrigger?
Prefer area over height. A single deeper pad spreads load more efficiently and more predictably than two thin pads stacked, because stacked interfaces can slide and the top pad can rock. If you must build height, use purpose-made cribbing plates rather than loose mats.
Send Us the Reaction Load and We Will Size the Pad
RUIYANG supplies HDPE crane pads and outrigger pads from 10 mm to 70–90 mm, rated 25–280 T, with a solid sealed core, dual-side anti-slip surface and factory-direct pricing. Give us the outrigger reaction, the float size and the ground condition and we will return a pad specification with area, thickness and loading. rdmats.com.
Discuss Your Crane Pad Project
Share the equipment, ground conditions, route dimensions, delivery location and required coverage. RUIYANG can review a suitable HDPE mat configuration for your project.
Website: rdmats.com