How to Calculate Load Capacity for Caster & Trolley Wheels

"Each castor is rated at 150 kg. Four castors. So the trolley is 600 kg capacity. Right?"

Wrong. This is the calculation error we see most often, and it is why so many trolleys fail early. This guide shows the real formula, how to pick a safety factor for Indian factory and warehouse conditions, a quick lookup chart, and five worked examples — based on Muvall's technical catalogue and our load testing.

The quick answer

For a 4-wheel trolley, the load rating you need on each wheel is:

Required rating per wheel = (load + trolley weight) × safety factor ÷ 3

For most hand-pushed warehouse trolleys (safety factor 1.5), that works out to roughly total load ÷ 3. A 600 kg trolley needs castors rated about 200 kg each, not 150 kg.

Why "4 × wheel rating" is wrong

Take a 4-wheel trolley with castors rated at 150 kg each:

4 wheels × 150 kg = 600 kg total capacity

This is the number on many trolley nameplates in India. It is also why those trolleys often last only few months before wheels deform, bearings wear out and the trolley becomes unreliable. The number assumes all four wheels share the load equally at all times. On a real floor, that never happens.

The 3-wheel rule (4-wheel trolleys only)

At any moment, one wheel of a 4-wheel trolley is often lightly loaded or off the ground:

• Floor unevenness — even a 2 mm height difference across the trolley footprint shifts load away from one wheel
• Frame flex — most fabricated trolley frames are not perfectly rigid; any twist redistributes load
• Off-centre loads — loads are rarely placed exactly in the middle
• Bumps and joints — speed bumps, expansion joints and floor transitions transfer weight as the trolley rolls over them

So on a 4-wheel trolley, the standard assumption is that only 3 of the 4 wheels carry the load. Dividing by 3 instead of 4 builds in a 33.3% margin of safety. This rule applies only to 4-wheel trolleys. For 3, 5, 6, 8 or any other number of wheels, divide by the actual number of wheels and let the safety factor provide the margin — chosen for the application, floor type, load type and speed.

The load capacity formula

W = (L₁ + L₂) × S ÷ n

• W = load rating required per wheel (kg)
• L₁ = maximum weight of the load (kg) — the peak, not the average
• L₂ = weight of the trolley or equipment itself (kg)
• S = safety factor (see the next section)
• n = number of wheels that carry the load (from the table above)

Round W up to the next standard castor rating. Never round down.

How to choose the safety factor

A castor's catalogue rating is a static load — what it holds standing still. A moving trolley also takes shocks when you start pushing, hit a bump or turn sharply. These dynamic loads can be 1.5 to 3 times the static load. The safety factor covers that. It is a rule of thumb: the right value changes with the application, floor type, load type and speed, which is why the table gives ranges.

When in doubt, use the higher end. Liquid loads shift as the trolley moves and stops, so treat them like a rougher condition. For a typical Indian warehouse trolley pushed by hand on decent concrete, S = 1.5 is a sound default; for rough factory floors or outdoor yards use 2.0 or more.

Caster wheel load capacity chart

Required rating per wheel for a 4-wheel trolley (calculated with 3 wheels). Total = load + trolley weight.

For other weights, wheel counts and conditions, use our Load Capacity Calculator. It takes your load, number of wheels, speed, load type, floor and usage, and works out the rating you need.

Worked examples

Example 1: Warehouse picking trolley

• Trolley frame: 40 kg
• Maximum payload: 200 kg
• Total: 240 kg
• Safety factor: 1.5 (general warehouse)
• W = 240 × 1.5 ÷ 3 = 120 kg per wheel
•  

Specify castors rated 125 kg or 150 kg. Anything less is undersized; much more just costs extra.

Example 2: Heavy pallet trolley for e-commerce

• Trolley frame: 100 kg
• Maximum pallet payload: 500 kg
• Total: 600 kg
• Safety factor: 1.5

• W = 600 × 1.5 ÷ 3 = 300 kg per wheel

   

Specify castors rated 300 kg or more. In Muvall's range, that is the MFTP series with 150 mm PUB wheels, or the HMP series with 150 mm PUCB wheels.

Example 3: 6-wheel heavy cart on an uneven shop floor

• Load: 2,000 kg
• Cart weight: 300 kg
• Total: 2,300 kg
• Wheels: 6, so calculate with 6 (the 3-wheel rule is only for 4-wheel trolleys)
• Safety factor: 2.0 (uneven floor)

• W = 2,300 × 2.0 ÷ 6 = 767 kg per wheel

   

Choose the next standard rating above 767 kg — in Muvall’s range, the HDP series (600–1,000 kg per castor) covers this. On a six-wheel cart the safety factor is doing all the work, so if the floor is very rough or the cart is moved quickly, go to the higher end of the range.

Example 4: Assembly-line engine trolley

• Trolley cradle: 200 kg
• Engine: 1,000 kg
• Tooling and fixtures: 100 kg
• Total: 1,300 kg
• Safety factor: 2.5 (assembly line with shock loads)

• W = 1,300 × 2.5 ÷ 3 = 1,083 kg per wheel

   

The HDP series (600–1,000 kg per castor) falls short here. The TTB series (1,500–2,000 kg per castor) is the right choice and gives a real margin for shock loads.

Example 5: Hospital stretcher

• Stretcher frame: 150 kg
• Heaviest patient: 150 kg (bariatric allowance)
• Mattress, rails, IV pole: 40 kg
• Total: 340 kg
• Safety factor: 2.5 (medical equipment)

• W = 340 × 2.5 ÷ 3 = 283 kg per wheel

   

That is more than many standard stretcher castors are rated for, so check the rating before you buy. Use medical-grade castors — quiet wheels and central locking — rather than an industrial series.

What your trolley is really rated for

Run the formula backwards to check an existing trolley:

Safe working load = wheel rating × n ÷ S

A 4-wheel trolley with 150 kg castors: 150 × 3 = 450 kg static. Divide by the safety factor: 450 ÷ 1.5 = 300 kg in a general warehouse, or 450 ÷ 2.0 = 225 kg on a rough factory floor. The "600 kg" trolley is really a 225–300 kg trolley.

Load is only the first check

Once you know W, match the rest of the castor to the job:

• Wheel material vs floor — PU wheels for concrete and epoxy; nylon or polypropylene for dry, smooth floors; UHMW for chemicals, food and pharma; phenolic or high-temperature glass-filled nylon for heat. More in Choosing the right trolley wheel material.
• Wheel diameter — larger wheels roll more easily over obstacles and need less push force; go larger for heavy loads and uneven floors.
• Bearings — double ball, tapered or thrust bearings cut starting resistance and handle higher dynamic loads.
• Castor body — forged or properly fabricated heavy-duty castors for high loads; pressed-steel bodies for light and medium duty. A strong wheel on a weak castor body still fails. For a full selection walk-through, see how to choose heavy-duty trolley wheels.
• Configuration — see 2 swivel + 2 fixed vs 4 swivel and how the right number of caster wheels eases heavy loads.

• Push–pull force — even with the right rating, a trolley that is too hard to push is a safety risk. Test a prototype before ordering in volume.

   

Common mistakes that cost money

1. Assuming all wheels share the load equally. Use the 3-wheel rule.
2. Skipping the safety factor. Castors rated exactly at the calculated load typically fail within 6–12 months.
3. Sizing to the average payload. If a trolley carries 200 kg on average but 350 kg at peak, size for 350 kg.
4. Forgetting the trolley's own weight. On fabricated trolleys, the frame can be 15–30% of the total.
5. Ignoring the floor. Rough floors, metal chips, speed bumps and expansion joints need a higher safety factor and the right wheel material.

6. Undersizing the bearings or castor body. The wheel rating only counts if the whole castor can take the load.

    

Checklist before you buy

1. Weigh the maximum load (L₁) and the trolley (L₂).
2. Count the wheels: for a 4-wheel trolley use n = 3; for any other number, n = the number of wheels.
3. Pick S from the safety factor table — the higher end if unsure.
4. Calculate W = (L₁ + L₂) × S ÷ n and round up to the next standard rating.
5. Choose the wheel material for your floor and environment.
6. Check wheel diameter, bearing type and castor body.
7. Confirm the top plate or stem fits your trolley.

8. Push-test a prototype before ordering in volume.

    

Bottom line

A 4-wheel trolley is not 4 times the wheel rating. It is 3 times the wheel rating, divided by a safety factor of usually 1.5–2.0. Undersizing leads to early wheel failure, frame damage and injuries when a trolley breaks on a slope or in a tight space. Oversizing costs a little more up front and buys years of reliable use.

Want a second opinion on a castor specification? Send us the trolley weight and payload, the floor type and the operating environment, and we will come back with a confirmed specification within a working day. Contact us · Product Finder · Trolley wheels manufacturer

Frequently asked questions

How do I calculate the load capacity of caster wheels? 

Add the load and the trolley weight, multiply by a safety factor, and divide by the number of load-bearing wheels: W = (L₁ + L₂) × S ÷ n. For a 4-wheel trolley use n = 3; for any other number of wheels, use the actual count.

Why divide by 3 for a 4-wheel trolley? 

Uneven floors, frame flex and off-centre loads mean one wheel is often lightly loaded or off the ground. Sizing for three wheels keeps the trolley safe when that happens.

What safety factor should I use for caster wheels?

 1.2–1.5 for light, slow carts on smooth floors; 1.5–2.0 for typical warehouse trolleys; 2.0–2.5 for rough factory floors and shock loads; 2.5–3.0 for medical, fast-moving or automated equipment.

What load capacity caster do I need for a 500 kg trolley? 

About 250 kg per wheel for a 4-wheel warehouse trolley (S = 1.5), or 333 kg per wheel on a rough floor (S = 2.0). Include the trolley's own weight in the 500 kg.

Is a 4-wheel trolley with 150 kg castors a 600 kg trolley? 

No. With the 3-wheel rule and a 1.5–2.0 safety factor, its safe working load is 225–300 kg.

Is there a quick rule of thumb? 

Yes: required rating per wheel ≈ total load ÷ 2. It applies to 4-wheel trolleys (calculated on 3 wheels) with a 1.5 safety factor, which suits most hand-pushed warehouse trolleys.

Does wheel size affect load capacity? 

Yes. Larger wheels usually carry more load, roll more easily over obstacles and need less push force, so go larger for heavy loads and uneven floors.