Weight comes from volume and density, and nothing else
A door slab is a box. Multiply width by height by thickness, divide by 1728 to get cubic feet, multiply by how heavy a cubic foot of the material is, and you have the weight. Everything interesting is hidden in that last number, because the same 32 by 80 slab can come out anywhere between about 29 and 96 pounds depending on what is inside it.
| Core | Density used here | A 32 x 80 x 1-3/8 slab |
|---|---|---|
| Hollow core | 14 lb/cu ft | 29 lb |
| Fiberglass entry over foam | 19 lb/cu ft | 39 lb |
| Insulated steel over foam | 24 lb/cu ft | 49 lb |
| Stile and rail softwood | 28 lb/cu ft | 57 lb |
| Solid particleboard core | 39 lb/cu ft | 79 lb |
| Solid hardwood | 45 lb/cu ft | 92 lb |
| Solid MDF | 47 lb/cu ft | 96 lb |
Those slab-only figures leave out hardware. The two entry-door rows are calculated at 1-3/8 for comparison even though those doors are normally 1-3/4, which is why the calculator asks for the thickness separately. And every one of these densities is a working estimate for a class of product, not a specification. If the manufacturer publishes a shipping weight for the exact slab, that beats anything on this page, and you can put it straight into the density field by dividing it back out — or just use it directly and skip the estimate.
Glass is heavier than the wood it replaces
Glass runs about 156 pounds per cubic foot, which works out to roughly 13 pounds per square foot per inch of thickness. A quarter inch of glass is about 3.25 pounds per square foot. A particleboard core at 39 pounds per cubic foot, at 1-3/8 thick, is about 4.5 pounds per square foot — so quarter inch glass in a solid core door is actually slightly lighter than what it replaced.
The direction flips completely on a hollow core. There, the slab material is around 1.6 pounds per square foot, so every square foot of glass roughly triples the local weight, and it does it out at the middle or the lock stile where the leverage is worst. A full-lite insulated unit in a hollow core skin is the combination that surprises people. Enter the total actual glass thickness, adding both panes of an insulated unit and ignoring the air space, because the air space is what makes the unit thick but contributes no weight.
The average per hinge is not what the top hinge feels
Dividing the weight by the hinge count gives a number that is easy to quote and easy to misuse. A door hangs off a vertical line of hinges and its centre of mass is half a door width away from that line, so the whole assembly wants to rotate. The top hinge resists that rotation in tension, trying to pull out of the jamb, while the bottom hinge is pushed into it. The middle hinge does comparatively little unless the slab is bowing.
That is why the calculator reports a moment as well as a weight. The moment is the weight times the horizontal distance to the slab centre, and it is the quantity that scales when you go from a 30 inch door to a 36 inch door of the same construction: the slab gets 20 percent heavier and the arm gets 20 percent longer, so the moment rises by about 44 percent. Nothing here says whether a particular hinge, screw or jamb can take it. That is a question for the hinge and door manufacturer, and for a fire-rated opening it is a question for the listing that opening was tested under, which is not something to work out from a calculator.
The screw length problem
Most hinges arrive with short screws. They are long enough to go through the hinge leaf and into the jamb, and that is all they were designed to do. Run the numbers: a 3/4 inch jamb with a 1/2 inch shim gap behind it means anything shorter than 1-1/4 inches never touches framing, and a 1-1/4 inch screw arrives exactly at the face of the trimmer with zero penetration. This is the default case on this page, and it is the standard condition in a great many houses.
For a hollow core slab it does not matter. For a solid slab it is the whole story of the sagging door: the jamb leg is being levered toward the opening by a hundred pound leaf, the shims are compressible, and the screws have nothing solid to resist against. The remedy carpenters use is to replace one or two screws per hinge with screws long enough to reach through the shim into the trimmer. The calculator tells you exactly how much longer they have to be before they even arrive at the wood.
Before you order anything
If the slab is going into an opening that is already framed, check the hole first with the rough opening calculator, and check what the door will actually leave you to walk through with the clear width calculator — nominal width and usable width are not the same number. If the jamb has to be replaced too, the jamb width calculator works out how wide it has to be for your wall. For heavier slabs on a sliding track rather than hinges, the pocket and barn door calculator covers the wall side of that decision, and lumber weight handles raw stock if you are building the slab rather than buying it.
One hazard worth naming without a procedure attached: a solid slab or an entry door coming off its hinges is a heavy, tall, top-loaded object that falls edge first. People get hands, feet and shins between a door and a floor every year. Plan how it comes down before you pull the last pin, and get a second person for anything over the weight you would comfortably carry up a ladder.
Questions people ask
How much does a solid core door weigh?
For a 32 by 80 slab at 1-3/8 thick with a solid particleboard core, this calculator gives about 79 pounds of slab plus whatever hardware is hanging on it. A 36 inch version of the same door is about 89 pounds. Solid hardwood and solid MDF run heavier again, in the 92 to 96 pound range at that size. Hollow core doors of the same dimensions come in around 29 pounds, which is why swapping one for the other in an existing jamb is a bigger change than it looks.
Do I need four hinges instead of three?
That is a question for the door and hinge manufacturer, not for arithmetic. What this page can tell you is the input to that question: the weight of the leaf, the moment it applies about the hinge line, and the average share per hinge. Hinge makers publish load and door-size limits per hinge size and gauge, and door makers specify how many hinges their slab is prepared for. Tall doors, heavy doors and doors with a closer on them are the cases where the published guidance changes, and on a fire-rated opening the hinge count is part of what the assembly was listed with and is not yours to change.
My door sags and rubs the strike. Is the door too heavy?
Usually the door is fine and the connection is not. Check the screws in the top hinge first: if they are the short ones that came in the box, they are holding in jamb stock and shims with air behind them, and the whole leaf is levering that jamb leg toward the opening. The calculator shows you how far a given screw actually reaches. Other common causes are a hinge leaf that has worked loose in its mortise, a jamb that was never shimmed solid at the hinges, and settlement in the framing above the head, which is a different problem entirely and shows up as the head jamb no longer being level.
Why does the glass thickness field say to add both panes?
An insulated glass unit is two panes with a sealed air or gas space between them. The unit might be 5/8 inch thick overall, but only the glass has mass. Two 1/8 inch panes is a quarter inch of actual glass no matter how wide the gap between them, so a quarter inch is what goes in the field. If you put the overall unit thickness in instead you will overstate the glass weight by roughly double.
Can I use this to check whether my header or wall can take the door?
No, and it is not close to the same question. A door leaf hangs from the jamb, the jamb is fastened to the trimmers, and the trimmers carry down to the plate. The weight of a door is small compared to what a header over that opening is carrying from the floor or roof above, so the header question is about the structure, not the door. The header and beam load calculator works out loads and reactions but deliberately does not size a member. Sizing is a span-table or engineer question in whatever code your jurisdiction has adopted.