Key takeaways
- Slide ratings are per pair, not per slide, and almost never per drawer assembly.
- A cabinet that rolls over cords and expansion joints sees shock loads a static test never applies.
- Front-biased weight in an extended drawer loads the slide far harder than the same weight spread evenly.
- The slide is only one of four limits: drawer box, cabinet frame and casters all have their own ceiling.
What the calculator is doing
The model is deliberately simple, because anything more elaborate would imply a precision the input data does not support:
working capacity = published pair rating
x service condition factor
x load position factor (if front biased)
x wear factor (if used slides)Every factor below 1.0 exists because the published number was measured under conditions your cabinet does not reproduce.
Where the derating factors come from
| Condition | Factor | What it accounts for |
|---|---|---|
| Fixed position, flat floor | 0.85 | Cabinet flex and slam loads only |
| Rolled on smooth concrete | 0.75 | Adds gentle rolling shock through the frame |
| Rolled over cords and joints | 0.62 | Each threshold is a small drop with the full drawer mass behind it |
| Rides in a truck or trailer | 0.45 | Repeated vertical acceleration, applied whether the drawer is open or shut |
| Front-biased load | x 0.85 | Weight in the front third of an extended drawer works the front bearing hardest |
| Worn or used slides | x 0.85 | Raceway wear, lost ball retention and play |
These are engineering guidance factors for planning, not manufacturer specifications. They are chosen to be conservative in the direction that costs you nothing: a drawer loaded to 70 percent of a derated figure has never been the reason a cabinet failed.
The four limits, not one
A drawer slide is the limit people quote because it is the number printed on the box. It is rarely the limit that bites first. Working from the tool outward, a loaded cabinet has four independent ceilings:
- The slide pair. What this calculator sizes.
- The drawer box. A thin drawer bottom deflects under a concentrated load long before
the slide complains. Sag that disappears when the drawer is closed is a drawer box problem.
- The cabinet frame. Total capacity is a structural claim about the shell, the welds and
the slide mounting points, all sharing the sum of every drawer.
- The casters. Usually the real ceiling on a rolling cabinet, and the one most often
quoted per caster rather than per set. See casters and mobility.
Size the drawer here, then check the whole cabinet against tool box load capacity and the tipping analysis in drawer weight distribution.
Typical drawer weights to sanity check your number
If you have not weighed anything yet, these approximate figures give you a starting estimate. Weigh the real drawer before you make a decision on it.
| Drawer contents | Approximate weight |
|---|---|
| 1/4 in and 3/8 in socket sets, SAE and metric, in trays | 20 to 35 lb |
| 1/2 in drive socket set with ratchet and extensions | 25 to 45 lb |
| Full 1/2 in impact socket set, shallow and deep | 45 to 80 lb |
| Combination wrench set, SAE plus metric, in organizers | 18 to 30 lb |
| Screwdrivers, pliers and cutters, one drawer | 15 to 25 lb |
| Air tools: impact, ratchet, die grinder, hoses | 30 to 55 lb |
| Torque wrenches, 3/8 and 1/2 in, in cases | 15 to 25 lb |
| Specialty automotive pullers and presses | 40 to 90 lb |