These tables contain comparative shelf sag measurements for 12″ deep shelves ranging in width from 30″ to 54″. Six types of shelving materials (all 3/4″ thick), three shelf loads (20, 30, 40 pounds per linear foot), and several shelf support techniques are represented. Sag measurements are to the nearest hundredth of an inch. As a general guideline, shelf sag should be 0.10″ or less.
8″ shelves | 12″ shelves | 16″ shelves | About these sag measurements
Shelf Width: 30″ (Optimal sag: 0.05″ or less, excessive: 0.13″+ )
| End Support | Front Support | Rear Support | Lbs per ft | Lbs total | MDF | Plywood | Pine | Poplar | Cherry | Oak |
| Float | No | No | 20 | 50 | .04 | .03 | .02 | .02 | .02 | .02 |
| Float | No | No | 30 | 75 | .08 | .05 | .03 | .03 | .03 | .03 |
| Float | No | No | 40 | 100 | .11 | .07 | .05 | .04 | .05 | .05 |
| Fixed | No | No | 20 | 50 | .04 | .03 | .03 | .02 | .02 | .02 |
| Fixed | No | No | 30 | 75 | .06 | .04 | .04 | .03 | .03 | .02 |
| Fixed | No | No | 40 | 100 | .07 | .05 | .05 | .04 | .04 | .04 |
| Fixed | Yes | No | 20 | 50 | .02 | .01 | .01 | .01 | .01 | .01 |
| Fixed | Yes | No | 30 | 75 | .03 | .01 | .01 | .01 | .02 | .01 |
| Fixed | Yes | No | 40 | 100 | .04 | .02 | .02 | .02 | .02 | .02 |
| Fixed | No | Yes | 20 | 50 | .03 | .03 | .03 | .02 | .02 | .02 |
| Fixed | No | Yes | 30 | 75 | .04 | .04 | .03 | .03 | .03 | .03 |
| Fixed | No | Yes | 40 | 100 | .05 | .05 | .05 | .04 | .04 | .04 |
| Fixed | Yes | Yes | 20 | 50 | .01 | .01 | .01 | .01 | .01 | .01 |
| Fixed | Yes | Yes | 30 | 75 | .01 | .01 | .01 | .01 | .01 | .01 |
| Fixed | Yes | Yes | 40 | 100 | .02 | .02 | .02 | .02 | .01 | .02 |
Shelf Width: 36″ (Optimal sag: 0.06″ or less, excessive: 0.18″+)
| End Support | Front Support | Rear Support | Lbs per ft | Lbs total | MDF | Plywood | Pine | Poplar | Cherry | Oak |
| Float | No | No | 20 | 60 | .14 | .07 | .04 | .05 | .06 | .05 |
| Float | No | No | 30 | 90 | .22 | .10 | .06 | .06 | .08 | .06 |
| Float | No | No | 40 | 120 | .32 | .14 | .10 | .09 | .11 | .08 |
| Fixed | No | No | 20 | 60 | .08 | .04 | .05 | .04 | .04 | .03 |
| Fixed | No | No | 30 | 90 | .12 | .06 | .06 | .05 | .05 | .04 |
| Fixed | No | No | 40 | 120 | .18 | .09 | .09 | .07 | .08 | .07 |
| Fixed | Yes | No | 20 | 60 | .04 | .02 | .02 | .02 | .02 | .02 |
| Fixed | Yes | No | 30 | 90 | .06 | .03 | .02 | .02 | .03 | .02 |
| Fixed | Yes | No | 40 | 120 | .09 | .05 | .04 | .03 | .04 | .03 |
| Fixed | No | Yes | 20 | 60 | .05 | .04 | .04 | .02 | .03 | .03 |
| Fixed | No | Yes | 30 | 90 | .06 | .05 | .05 | .04 | .04 | .04 |
| Fixed | No | Yes | 40 | 120 | .08 | .07 | .07 | .05 | .05 | .05 |
| Fixed | Yes | Yes | 20 | 60 | .02 | .01 | .01 | .01 | .02 | .01 |
| Fixed | Yes | Yes | 30 | 90 | .03 | .02 | .02 | .02 | .02 | .02 |
| Fixed | Yes | Yes | 40 | 120 | .05 | .03 | .03 | .03 | .03 | .03 |
Shelf Width: 42″ (Optimal sag: 0.07″ or less, excessive 0.21″+)
| End Support | Front Support | Rear Support | Lbs per ft | Lbs total | MDF | Plywood | Pine | Poplar | Cherry | Oak |
| Float | No | No | 20 | 70 | .28 | .13 | .08 | .07 | .08 | .07 |
| Float | No | No | 30 | 105 | .43 | .18 | .15 | .13 | .12 | .10 |
| Float | No | No | 40 | 140 | .58 | .24 | .21 | .17 | .17 | .13 |
| Fixed | No | No | 20 | 70 | .15 | .10 | .09 | .06 | .08 | .05 |
| Fixed | No | No | 30 | 105 | .22 | .15 | .14 | .10 | .10 | .09 |
| Fixed | No | No | 40 | 140 | .30 | .20 | .18 | .13 | .13 | .12 |
| Fixed | Yes | No | 20 | 70 | .07 | .05 | .04 | .03 | .04 | .04 |
| Fixed | Yes | No | 30 | 105 | .11 | .06 | .07 | .05 | .05 | .05 |
| Fixed | Yes | No | 40 | 140 | .16 | .10 | .10 | .08 | .07 | .06 |
| Fixed | No | Yes | 20 | 70 | .08 | .07 | .07 | .05 | .05 | .05 |
| Fixed | No | Yes | 30 | 105 | .11 | .11 | .09 | .08 | .07 | .07 |
| Fixed | No | Yes | 40 | 140 | .13 | .13 | .12 | .10 | .09 | .09 |
| Fixed | Yes | Yes | 20 | 70 | .04 | .03 | .03 | .03 | .02 | .02 |
| Fixed | Yes | Yes | 30 | 105 | .05 | .04 | .04 | .04 | .03 | .03 |
| Fixed | Yes | Yes | 40 | 140 | .07 | .05 | .05 | .05 | .05 | .04 |
Shelf Width: 48″ (Optimal sag: 0.08″ or less, excessive: 0.24″+)
| End Support | Front Support | Rear Support | Lbs per ft | Lbs total | MDF | Plywood | Pine | Poplar | Cherry | Oak |
| Float | No | No | 20 | 80 | .48 | .16 | .14 | .14 | .14 | .12 |
| Float | No | No | 30 | 120 | .76 | .30 | .23 | .24 | .21 | .17 |
| Float | No | No | 40 | 160 | 1.04 | .39 | .34 | .30 | .29 | .23 |
| Fixed | No | No | 20 | 80 | .23 | .12 | .12 | .11 | .10 | .08 |
| Fixed | No | No | 30 | 120 | .36 | .19 | .19 | .17 | .16 | .14 |
| Fixed | No | No | 40 | 160 | .49 | .26 | .25 | .22 | .21 | .18 |
| Fixed | Yes | No | 20 | 80 | .14 | .06 | .07 | .04 | .04 | .03 |
| Fixed | Yes | No | 30 | 120 | .22 | .11 | .11 | .08 | .08 | .06 |
| Fixed | Yes | No | 40 | 160 | .30 | .16 | .15 | .12 | .11 | .08 |
| Fixed | No | Yes | 20 | 80 | .10 | .10 | .09 | .08 | .08 | .06 |
| Fixed | No | Yes | 30 | 120 | .13 | .16 | .13 | .11 | .10 | .09 |
| Fixed | No | Yes | 40 | 160 | .16 | .20 | .17 | .14 | .13 | .12 |
| Fixed | Yes | Yes | 20 | 80 | .06 | .04 | .04 | .03 | .03 | .03 |
| Fixed | Yes | Yes | 30 | 120 | .08 | .07 | .06 | .05 | .07 | .05 |
| Fixed | Yes | Yes | 40 | 160 | .10 | .09 | .08 | .07 | .08 | .07 |
Shelf Width: 54″ (Optimal sag: 0.09″ or less, excessive: 0.27″+)
| End Support | Front Support | Rear Support | Lbs per ft | Lbs total | MDF | Plywood | Pine | Poplar | Cherry | Oak |
| Float | No | No | 20 | 90 | .70 | .27 | .27 | .20 | .22 | .16 |
| Float | No | No | 30 | 135 | 1.23 | .50 | .44 | .34 | .34 | .25 |
| Float | No | No | 40 | 180 | 1.8 | .69 | .60 | .46 | .47 | .34 |
| Fixed | No | No | 20 | 90 | .31 | .20 | .18 | .14 | .14 | .12 |
| Fixed | No | No | 30 | 135 | .55 | .35 | .29 | .23 | .22 | .18 |
| Fixed | No | No | 40 | 180 | .84 | .44 | .41 | .33 | .32 | .26 |
| Fixed | Yes | No | 20 | 90 | .13 | .09 | .09 | .08 | .05 | .05 |
| Fixed | Yes | No | 30 | 135 | .25 | .19 | .14 | .14 | .11 | .10 |
| Fixed | Yes | No | 40 | 180 | .40 | .28 | .21 | .20 | .19 | .15 |
| Fixed | No | Yes | 20 | 90 | .09 | .15 | .13 | .10 | .08 | .08 |
| Fixed | No | Yes | 30 | 135 | .14 | .22 | .18 | .15 | .14 | .11 |
| Fixed | No | Yes | 40 | 180 | .18 | .28 | .23 | .18 | .19 | .15 |
| Fixed | Yes | Yes | 20 | 90 | .05 | .06 | .08 | .06 | .03 | .04 |
| Fixed | Yes | Yes | 30 | 135 | .08 | .12 | .19 | .09 | .07 | .08 |
| Fixed | Yes | Yes | 40 | 180 | .11 | .18 | .15 | .12 | .10 | .10 |
