Caster Load Ratings vs Real differ by load capacity, wear behavior, and floor compatibility.
- Match capacity per caster to your total load divided by 3 (one caster may be airborne)
- Polyurethane and rubber wheels favor floor protection; phenolic and steel favor heavy capacity
- Top-plate or stem mount is dictated by the equipment, not preference
- CasterHQ stocks Albion, Hamilton, P&H, Colson, Faultless, and Durastar from Mansfield, Texas
- Call 844-439-4335 for fitment help on any non-standard caster
On this page
- Caster Load Ratings vs Duty Cycles: The 2026 Engineering Reference
- What Is a Caster Load Rating
- Duty Cycle Categories
- Matching Load to Duty Cycle
- Derating for Real-World Conditions
- Application Examples by Duty Cycle
- Load vs Duty Cycle Math (Worked Formula)
- Spec Checklist Before You Order
- Frequently asked questions
- Related Engineering Tools & Guides
Caster Load Ratings vs Duty Cycles: The 2026 Engineering Reference
A caster's load rating is what it can carry. Its duty cycle is how often, how long, and how hard it has to work. Spec based on the first alone and the caster fails within months. This guide maps ICWM load ratings to real-world duty cycles so you size a caster that survives the full service life, not just the load test.
In this guide
What Is a Caster Load Rating
Load rating is the maximum weight a single caster can support under controlled test conditions, per ICWM and ANSI MH31.1 test standards. It's the starting point for spec selection, not the final answer.
- Static load rating: maximum weight under parked conditions on level floor.
- Dynamic load rating: maximum weight while rolling at walking speed on smooth floor.
- Shock load rating: additional capacity margin for floor discontinuities, impacts, and starts/stops.
- Published rating assumes ideal conditions: smooth floor, moderate temperature, rated speed, straight-line travel.
Duty Cycle Categories
Duty cycle measures how often the caster rolls, how long per event, and how far. Four standard categories cover the industrial range.
| Duty Cycle | Rolling Time | Events per Shift | Typical Application | Service Life (Years) |
|---|---|---|---|---|
| Intermittent | < 2 hrs/shift | 5-20 | Office, light assembly | 8-12 |
| Moderate | 2-4 hrs/shift | 20-100 | Cart fleet, warehouse | 5-8 |
| Heavy | 4-6 hrs/shift | 100+ | Tow line, continuous rolling | 3-5 |
| Continuous | > 6 hrs/shift | Always rolling | AGV, AMR, production line | 2-4 (replace on schedule) |
Matching Load to Duty Cycle
The right spec uses load rating as a starting number and derates based on duty cycle. The shorter the duty cycle, the closer to rated you can run. Continuous duty requires significant derating.
- Intermittent duty: run at 80-90% of rated capacity.
- Moderate duty: run at 65-75% of rated capacity.
- Heavy duty: run at 50-60% of rated capacity.
- Continuous duty: run at 35-50% of rated capacity; consider next-size-up rig.
Derating for Real-World Conditions
Apply additional derating factors when real-world conditions depart from the ICWM test baseline.
| Condition | Derating Factor | Rationale |
|---|---|---|
| Smooth indoor concrete | 1.0 (baseline) | ICWM test condition |
| Expansion joints every 20 ft | x 0.8 | Shock load increase |
| Unsealed/dusty concrete | x 0.85 | Bearing life decrease |
| Outdoor asphalt/composite | x 0.7 | Irregular surface shock |
| Speed over 3 mph | x 0.8 | Heat build-up in bearings |
| Temperature over 100°F | x 0.9 | Tread compound softening |
| Temperature below -20°F | x 0.85 | Compound brittleness |
Application Examples by Duty Cycle
Four worked examples showing load/duty cycle matching in practice.
- Office furniture (intermittent): 250 lb cart, low duty. Spec at 80% rated - any 350 lb caster works. Light-duty cart rig fine.
- Warehouse pick cart (moderate): 1,000 lb cart, moderate duty, smooth concrete with joints. 1,000 lb / 0.75 / 0.8 = 1,670 lb per caster minimum. Industrial rig required.
- Tow line (heavy): 3,000 lb load, heavy duty, rough concrete. 3,000 lb / 0.55 / 0.7 = 7,800 lb per caster minimum across a 4-caster tow cart. Heavy industrial or kingpinless forged.
- AGV continuous: 800 lb load, continuous duty, smooth epoxy-coated floor. 800 lb / 0.4 = 2,000 lb per caster minimum. Oversized for load to guarantee 10+ year bearing life.
Load vs Duty Cycle Math (Worked Formula)
The complete caster sizing formula.
Required Load Rating = (Cart Load / Duty Factor) / (Product of all Derating Factors)
- Cart Load: loaded weight divided by 3 (not 4) to account for uneven floor distribution on 4-caster carts.
- Duty Factor: 0.85 intermittent, 0.70 moderate, 0.55 heavy, 0.40 continuous.
- Derating Factors: floor, speed, temperature, environment multiplied together.
- Round up: to next-larger standard caster size.
Spec Checklist Before You Order
Six data points produce a correctly-sized caster on the first RFQ.
- Cart total weight (loaded): including heaviest payload.
- Duty cycle category: intermittent, moderate, heavy, or continuous.
- Floor condition: smooth, jointed, unsealed, outdoor.
- Travel speed (mph): walking 3 mph, tow 5 mph, AGV 2-4 mph typical.
- Environment: indoor/outdoor, temperature range, washdown.
- Required service life: in years before planned replacement.
Key takeaways
- Load rating is the ceiling under ideal conditions; real applications derate 30-65% based on duty cycle and environment.
- Continuous-duty AGV applications run at 35-50% of rated capacity for 10+ year bearing life.
- Divide cart load by 3 (not 4) to size per-caster capacity; one caster is always partly unloaded.
- Stack derating factors multiplicatively: floor condition, speed, temperature, environment.
- Intermittent duty lets you run 80-90% of rated; heavy/continuous duty drops to 55% or less.
Frequently asked questions
What's the difference between load rating and capacity?
Load rating is the tested maximum under controlled conditions (ICWM or ANSI MH31.1). Capacity, as commonly spoken, is the practical working load in your application after derating for duty cycle and environment. Load rating and capacity are often the same number on a spec sheet, but practical capacity is always lower.
Can I use load rating x 4 for the cart total?
No. Divide cart loaded weight by 3 to size per-caster capacity. Floor unflatness, uneven load placement, and cornering consistently put 30-40% more than theoretical share on individual casters at some point in the service cycle.
What's the derating for 24/7 continuous operation?
Run at 35-50% of rated capacity, and consider stepping one duty class up. A 1,500 lb rated caster on 24/7 continuous duty should not carry more than 600-750 lb per caster. For high-value applications (AGV, production), oversizing to 35-40% of rated extends bearing life significantly.
Do shock load rating and dynamic load rating apply differently?
Yes. Dynamic rating applies to continuous rolling load. Shock rating provides additional margin for discontinuities and impacts. On joint-heavy or outdoor surfaces, derate below dynamic rating AND ensure shock rating is at least 1.5x the worst-case impact load.
How do I know my actual duty cycle if it varies?
Use the highest-duty condition, not the average. If the cart runs intermittent most days but has moderate-duty weeks during inventory cycles, spec for moderate duty. Seasonal and occasional peak duty drives wear faster than average duty.
Is oversizing casters always better?
Not always. Oversizing beyond 2x rated load adds cost, increases mounting height, and in some cases hurts rolling performance because the wheel doesn't deform enough for traction. Target 1.25-1.5x the derated application load for most industrial applications; up to 2x for continuous AGV.
Spec Casters to Duty Cycle, Not Just Load
CasterHQ engineers match casters to duty cycle, floor, speed, and environment daily. Send your cart weight, duty cycle, and application details. We return a correctly-derated spec that survives the real-world service life.
References & Standards Cited
- Institute of Caster and Wheel Manufacturers (ICWM) load rating standards, 2024 edition
- ANSI MH31.1 caster and wheel testing standard
- CasterHQ 2024-2025 customer service-life data across 38,000+ industrial carts
- Hannibal Industries tow line caster engineering bulletin, 2023
- Albion Industries duty-cycle derating reference, 2024
- CasterHQ bearing-life field study, 2022-2025
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Shop All CastersCall 844-439-4335Jordan Wilson
Founder of CasterHQ.com. Works directly with engineers, MRO buyers, and procurement teams across material handling, healthcare, food service, aerospace, and OEM. CasterHQ stocks Albion, Hamilton, P&H, Colson, Faultless, and the in-house Durastar series from a Texas warehouse and retrofits OEM fitments from dimensional drawings when brands discontinue parts.