By Craig Dunstan, Brisbane
A 200kg or 300kg per-shelf rating means one shelf can safely carry that much weight when the load is spread evenly across the whole shelf surface — not stacked in one spot. The per-shelf figure is the number to shop on; the "total unit" figure (800kg for Steel Power Shelving's 200kg light-duty line, 1,200kg for its 300kg heavy-duty line) is simply the per-shelf rating multiplied across the unit's load-bearing shelves. Once you understand those two ideas — evenly distributed load, and per-shelf versus total — choosing between the two lines takes about five minutes.
This guide explains both ideas in plain terms, gives realistic weight benchmarks for common garage items, and shows exactly when to step up from 200kg to 300kg per shelf.
"Evenly distributed" is doing a lot of work in that rating
Every honest shelving rating assumes an evenly distributed load: the weight spread across the full shelf area, so every support point carries its share. That is how most real garage storage naturally sits — rows of tubs, boxes side by side, bins across the shelf.
A point load is the opposite: the same weight concentrated on one small spot, like a single dense machine placed dead centre. Concentrated weight stresses the middle of the shelf far more than the same kilograms spread out, so a shelf that comfortably carries its rating as boxes may sag under one centred lump of cast iron. Two practical habits follow:
- Spread heavy items out. Place dense items over the shelf's supported edges and corners rather than dead centre, and split a heavy load across the shelf area where you can.
- Treat the rating as a ceiling for spread loads, not a promise for concentrated ones. If one very heavy item dominates a shelf, leave a bigger margin below the rated figure.
Per-shelf vs total unit: the simple maths
Steel Power Shelving publishes both numbers for its garage shelving range, and the relationship is straightforward multiplication across four load-bearing shelves:
| Line | Per shelf | Load-bearing shelves | Total per unit | Depth |
|---|---|---|---|---|
| Light-duty | 200kg | 4 | 800kg | 0.5m |
| Heavy-duty | 300kg | 4 | 1,200kg | 0.6m |
Two things follow from the maths. First, a big total figure never means one shelf can take it all — 1,200kg total is still 300kg per shelf, full stop. Second, when you compare brands, compare per-shelf numbers; a competitor's headline total divided by its shelf count is often a much smaller per-shelf figure than the advertising suggests.
What garage items actually weigh
You rarely need scales — common items have well-known approximate weights. These are rough, typical figures to help you estimate a shelf load, not measurements of any particular product:
- A full archive or moving box: roughly 10–15kg
- A bag of potting mix or cement: typically sold around 20–25kg
- A 20-litre container of liquid: roughly 20kg, plus the container
- A car battery: typically around 15–20kg
- A loaded steel toolbox: roughly 20–40kg
- A large filled plastic storage tub: commonly 15–30kg
Run the numbers on your heaviest planned shelf. Six full archive boxes come to roughly 60–90kg — comfortably inside a 200kg shelf. A shelf of automotive gear — a couple of batteries, a loaded toolbox, fluids and parts bins — can plausibly reach 150–250kg territory, which is exactly where the 300kg line earns its keep.
Choosing between the 200kg and 300kg lines
Choose the light-duty line (200kg per shelf, 800kg per unit) if:
- You are storing household overflow: boxes, tubs, camping and sporting gear, garden supplies.
- Your loads are bulky rather than dense, and no single shelf will sit anywhere near 200kg.
- The 0.5m depth suits your space — it is the friendlier depth beside a parked car.
Choose the heavy-duty line (300kg per shelf, 1,200kg per unit) if:
- You are storing tools, automotive parts, fluids or dense boxed stock.
- Any single shelf could regularly sit above about 150kg — the margin is worth it.
- You want the deeper 0.6m shelf so bulky items sit squarely, and the taller options: the heavy-duty line comes in 1.8m, 2.0m and 2.4m heights and 1.5m and 2.0m widths, in powder-coated steel with height-adjustable shelves.
Mixing lines is completely normal — heavy-duty on the tool wall, light-duty for household storage. Whichever you choose, keep the heaviest shelf low, and pair open shelving with a lockable unit from the metal cabinet range for power tools and chemicals. For a deeper look at the per-shelf versus total-unit trap across the wider market, see how much weight a garage shelf can hold.
FAQ
Q: What does a 300kg per shelf rating actually mean?
A: It means one shelf can safely carry up to 300kg when that weight is spread evenly across the whole shelf surface. It is not a promise for the same weight concentrated in one spot, and it never means the whole unit's total can sit on a single shelf.
Q: What is the difference between evenly distributed load and point load?
A: An evenly distributed load is spread across the full shelf — rows of boxes or tubs — so every support point shares the weight. A point load concentrates the same kilograms in one small spot, which stresses the shelf centre far more. Shelving ratings assume the evenly distributed case, so spread dense items out and leave extra margin for concentrated ones.
Q: How do per-shelf and total unit ratings relate?
A: Total unit capacity is the per-shelf rating multiplied by the number of load-bearing shelves. Steel Power Shelving's light-duty line is 200kg per shelf across four load-bearing shelves, giving 800kg per unit; the heavy-duty line is 300kg per shelf, giving 1,200kg per unit. Always compare brands on the per-shelf figure.
Q: How heavy are typical garage items?
A: As rough, common-knowledge figures: a full archive box is roughly 10–15kg, a bag of potting mix or cement typically 20–25kg, a car battery around 15–20kg, a loaded toolbox roughly 20–40kg, and a large filled storage tub commonly 15–30kg. Adding up your heaviest planned shelf against these benchmarks tells you which line you need.
Q: When should I pay extra for the 300kg line?
A: When any single shelf could regularly sit above about 150kg — tools, automotive parts, fluids or dense boxed stock — or when you want the deeper 0.6m shelf and taller 1.8m, 2.0m or 2.4m frame options. For bulky-but-light household storage, the 200kg line is usually all you need.
Q: Can I load one shelf to the maximum and leave the rest empty?
A: Yes — each shelf's rating stands on its own, so a single shelf can carry its full rated load (evenly distributed) regardless of the others. For stability and safety, though, always put the heaviest shelf low in the unit and leave a sensible margin rather than living at the limit.