The glass is not the heavy part until the frame gets big
On the default 16 by 20 in a 1-1/2 inch moulding, the breakdown is 2.31 pounds of glazing, 1.04 of mats, 0.23 of backing, 3.76 of moulding, 0.40 of artwork and 0.15 of hardware — 7.89 pounds, with the moulding as the single heaviest component at 48 percent of the frame.
That surprises people, and the reason is geometry rather than materials. Glazing weight goes with the area of the package, so it grows as the square of the size. Moulding weight goes with the perimeter, so it grows in a straight line. With the figures in this form the two cross at roughly 27.7 inches square: below that the moulding wins, above it the glazing does, and by 40 inches square the glass is half as heavy again as the moulding — 11.56 pounds against 7.79.
The practical version: a wall of small frames is a wall of wood, and a single large piece is a sheet of glass with a bit of wood round it. They want thinking about differently, and the moulding weight per foot is the input that swings the small end hardest — a hardwood profile and a light composite of the same shape are not close.
Where the numbers come from, and where they do not
Everything in this page is your input. The glazing density field starts at 156 pounds per cubic foot because soda-lime glass works out near there and 74 for acrylic, but both are placeholders for whatever your supplier tells you, and the page states neither as fact. Mat board and backing vary enough between makes that a borrowed figure is close to worthless: weigh a full sheet on a kitchen scale and divide by its volume, and you have a number good for every job you do with that board.
The moulding figure is the one worth measuring properly, because it dominates the small end and because published profile weights are given per foot of stock rather than per foot of finished frame. Weigh a two foot offcut and double it. If you cannot, the ratio between profiles is more stable than the absolute figures — a profile twice the cross-section is roughly twice the weight in the same material.
Components that add up to the total shown
The six lines in the breakdown are each rounded to a hundredth of a pound and the total is the sum of those rounded figures rather than a separately rounded sum. That means the column on the page adds up exactly as printed, which is not true of most breakdowns and is the sort of thing that costs half an hour when it is not true.
It also means the total can differ from an exact calculation by a couple of hundredths on a large stack. That is the right trade: a printed column that does not add up looks like an error even when it is not, and two hundredths of a pound is nothing anybody is going to notice on a wall.
Weight per hanger is division, not a verdict
The page divides the frame weight by the number of hangers and restates whatever rating you typed in beside it. That is all it does, and the wording is deliberate. Whether a hanger holds a picture is not a question about the picture. It is a question about the specific hardware, about how the load actually shares between two hooks — which is not evenly, if one is a fraction lower than the other — and above all about what is behind the plaster at that exact point.
Name the hazards and stop there. A framed piece coming off a wall lands on whatever is beneath it and it is mostly glass. Large framed work is a two-person lift both directions. Anchors in drywall alone are the ones that let go, and they tend to let go weeks later rather than while you are still holding the frame. None of those have a procedure on this page, and the specification for a fixing comes from the manufacturer and from whoever knows the wall.
Shipping and moving a run
The run total is the number that matters for a box or a van rather than the per-frame figure. Ten of the default frames is 78.9 pounds of framed work, which is not a heavy load until you remember it is spread over ten fragile flat objects that cannot be stacked flat without pressure on the glass.
The glazing swap is where a run changes character. Moving from the 156 default to the 74 alternative takes 1.21 pounds off each of the default frames, which is 15.3 percent of the frame. Across ten frames that is 12.1 pounds and, more to the point, ten sheets that do not shatter in transit. What that swap costs in every respect other than weight is not something this page has any view on.
Questions people ask
How much does a framed 16 by 20 picture weigh?
With the placeholder figures in this form, 7.89 pounds: 2.31 of glazing, 1.04 of mats, 0.23 of backing, 3.76 of moulding, 0.40 of artwork and 0.15 of hardware. Every one of those is a number you can change, and the moulding figure is the one that moves the answer most at this size, since a hardwood profile and a light composite of the same shape are not remotely the same weight. Weigh an offcut rather than borrowing a number.
Is the glass the heaviest part of a framed picture?
Only on larger pieces. Glazing weight follows the area and moulding weight follows the perimeter, so the balance shifts with size. With the default figures they are equal at roughly 27.7 inches square — under that the moulding is the heavier half, over it the glazing is, and at 40 inches square the glazing is about half as heavy again. On the default 16 by 20 the moulding is 48 percent of the frame and the glazing 29.
How much lighter is acrylic than glass?
It depends entirely on the two densities you enter and the page asserts neither. With the placeholders in the form — 156 against 74 pounds per cubic foot — the glazing in the default 16 by 20 drops from 2.31 pounds to 1.10, taking the whole frame from 7.89 to 6.68, which is 15.3 percent off. Everything else about that decision, including cost, scratching and what either material does or does not filter, is outside this page and is not implied by the weight figure.
Will my hanger hold this?
This page will not answer that and no calculator should. It divides the weight by the number of hangers and restates the rating you typed in from the packet, side by side and labelled as reported rather than judged. Whether a given hook holds a given picture depends on the specific hardware, on how unevenly two hooks actually share a load, and above all on what is behind the wall at that point — a stud, plaster, or nothing. That is a question for the hardware manufacturer and for whoever knows the wall.
Why does the breakdown round each part to a hundredth?
So the column adds up as printed. Each of the six components is rounded to a hundredth of a pound and the total is the sum of those rounded numbers, rather than an independently rounded exact total. The cost is that the printed total can sit a hundredth or two off a full-precision calculation; the benefit is that a column which does not add up never appears, and a breakdown that does not reconcile reads as a bug whether or not it is one.