Picture frame molding calculator.
Box sizes, four miter lengths each, and what to buy.
Box width = (wall width − 2 × margin − (n − 1) × gap) ÷ n, and the same division down the field between baseboard and cap. Each box is four pieces mitered at 45°: the long point equals the box side, the short point is two molding widths less.
0302 / What to cut
- Proportion
- 0.73 : 1 (height to width)
- Blocked boxes
- none
- Molding in total
- 35.8 linear ft
- Field area
- 30.8 sq ft
- Sticks to buy
- 6 × 8 ft
Set the miter saw stop to the long point. The short point is what you will see on the wall, and it takes care of itself.
0203 / Your wall
TO SCALE| Box | From left | Top from floor | Size | Lands on |
|---|---|---|---|---|
| R1 · 1 | 4″ | 2′ 8″ | 31″ × 22 3/4″ | |
| R1 · 2 | 3′ 3″ | 2′ 8″ | 31″ × 22 3/4″ | |
| R1 · 3 | 6′ 2″ | 2′ 8″ | 31″ × 22 3/4″ | |
| R1 · 4 | 9′ 1″ | 2′ 8″ | 31″ × 22 3/4″ |
Four cuts per box, two lengths each.
A mitered piece is longer on the face than on the back. The long point is the face length and the number you set on the saw; the short point is the back. They differ by twice the molding width, and confusing them is how a box ends up short on both sides.
| Side | Qty | Long point | Short point |
|---|---|---|---|
| top and bottom | 8 | 31″ | 29″ |
| sides | 8 | 22 3/4″ | 20 3/4″ |
The cutting plan
8 ft sticks — 5 to cut plus 1 spare, 6 to buy. Chosen on molding bought: 48 ft, where 10 ft sticks add up to 50 ft. first-fit decreasing, one kerf charged between two cuts on the same stick; workable, not proven optimal.
| Stick | Cuts | Offcut |
|---|---|---|
| Stick 1 | box rail 31″ · box rail 31″ · box rail 31″ | 2 3/4″ |
| Stick 2 | box rail 31″ · box rail 31″ · box rail 31″ | 2 3/4″ |
| Stick 3 | box rail 31″ · box rail 31″ · box stile 22 3/4″ | 11″ |
| Stick 4 | box stile 22 3/4″ · box stile 22 3/4″ · box stile 22 3/4″ · box stile 22 3/4″ | 4 5/8″ |
| Stick 5 | box stile 22 3/4″ · box stile 22 3/4″ · box stile 22 3/4″ | 27 1/2″ |
Which stick length to buy
| Stock length | Sticks | Offcut | Offcut total |
|---|---|---|---|
| 8 ft least molding bought | 6 | 10.4 % | 4′ 5/8″ |
| 10 ft | 5 | 10.4 % | 4′ 1/2″ |
| 12 ft | 5 | 25.3 % | 12′ 1/2″ |
| 16 ft | 4 | 25.3 % | 12′ 3/8″ |
Seen in stock on 2026-09-09: 8, 10, 12 feet. A length we have not seen is compared but never recommended.
The division, then the miter
A wall of boxes is two divisions and one cut angle. Across: the wall, less two margins and the gaps, shared between the boxes. Down: the field between the baseboard and the cap, less the top and bottom margins, shared between the rows. Then every box is four pieces at 45°.
Worked example: a 12-foot wall, four boxes
Wall 144 inches wide, 4-inch margins at both corners, 4 inches between boxes, four boxes across:
- Margins and gaps take 2 × 4 + 3 × 4 = 20 inches.
- 144 − 20 = 124, over four boxes: 31 inches wide each.
- Field: the underside of the chair rail at 36 inches, less a 5¼-inch baseboard, leaves 30¾ inches.
- Less a 4-inch margin top and bottom: the box is 22¾ inches tall.
- In 1-inch molding, the long points are 31 and 22¾; the short points are 29 and 20¾.
That box is 0.73 as tall as it is wide. Boxes read best a little taller than wide, so on this wall five boxes — 24 inches, ratio 0.95 — or a second row would both be closer to it. The calculator reports the ratio and leaves the decision alone.
How much extra to buy, and why nobody agrees
Google's summary of this topic tells searchers to add 10 to 15 %. It is not wrong, but it is flattened: the trade source we checked refuses a single number and gives bands instead. The rate depends on the FINISH, not only on the length: primed stock can be patched with filler, prefinished stock cannot. In its own words: “It depends on how good your installers are. I would figure 5-10%. If it is paint grade that is just primed and will be painted on site then you would be in the 5% area as mistakes can be hidden with putty or caulk. If it is pre-painted or stained and finished you would probably be around the 10% mark.”
| Case | Allowance | Status |
|---|---|---|
| paint grade primed, few miters, long runs | 5–10 % | Convention |
| typical job, mid-range home | 10–15 % | Convention |
| pre-finished or stained | 10–15 % | Convention |
The source names miters as the factor: its lower band is for runs with “not many miters”. A wall of picture frames is the opposite case — four per box, and each one is a chance to lose a piece. Twelve boxes is forty-eight miters. That is why we place it in the 10–15 % band rather than below it; the placement is our reading of the source, not a figure it states for picture frames.
Margins are not gaps
A mistake to avoid here is forcing the corner margin to equal the gap between boxes. They do different jobs: the gap sets the rhythm, the margin decides how the run meets the corner — and a wall ending against a door casing wants a different margin from one dying into an open corner. Both are separate inputs above.
What an outlet does to a layout
Nothing, until it lands inside a box — and then it is a decision, not a calculation. Enter it as an obstacle: the box it touches is hatched and dropped from the cut list. Shifting the run so the outlet falls in a gap, accepting one shorter box, or leaving that box out are all yours to pick. What the page will not do is move one box and leave the rest unevenly spaced.
Before you cut
How to calculate picture frame molding?
Take the wall width, subtract the two side margins and the gaps between boxes, then divide what is left by the number of boxes. Do the same down the wall between the baseboard and the cap. Each box then needs four pieces cut at 45 degrees, and the length you set on the saw is the long point.
How to map out picture frame molding?
Mark the field first — baseboard up, cap down, margins in — then the box positions from the left corner, cumulatively, never off the previous mark. The table under the drawing gives every box from the left edge and from the floor, so the layout can be pencilled before anything is cut.
What size should picture frame molding be?
Profile widths vary by product, and we have not measured any ourselves. One tool in this search offers two, 1 inch and 1.57 inches (4 cm); enter the width of the molding you actually bought. The box itself has no standard size: it is whatever the wall divides into, which is why this page reports the height-to-width ratio and warns when a box comes out square.
How far apart should picture frame molding be?
Between 3 and 6 inches is what the ranking pages and Google's own summary use, and the margin at the wall does not have to match the gap between boxes. Set them separately here; the drawing shows what each choice does before you commit.
Is this picture frame molding calculator free?
Yes. Box sizes, miter lengths, the elevation drawing, the cut list, the stick comparison, CSV and print. No sign-up, no email, nothing kept back.
Is there an app for it?
There is nothing to install: this runs in a phone browser, on your device, and the plan prints or exports so the numbers reach the wall without the phone.
Is this the same thing as a wall box molding calculator?
Yes. Box trim, box molding, shadow box, picture frame molding — the same applied frames under different names. If you are looking for a general wall molding calculator, this handles anything laid out as boxes between a baseboard and a cap or a ceiling.
What are the usual picture frame molding measurements?
There are no usual box measurements, and any page that gives you some is describing its own wall. What is reusable is the method and the profile widths. Enter your wall and read the ratio: boxes a little taller than wide are the common choice, and this page says so when yours come out square.
How is this different from picture frame wainscoting?
Same moldings, different question. Wainscoting stops at a cap around a third of the way up the wall; picture frame molding often runs the full height. Untick the chair rail here and the field runs to the ceiling. For the cap-height side of it, the wainscoting calculator carries the sourced heights.
What if an outlet or a switch lands inside a box?
Enter it as an obstacle. The box that overlaps is drawn hatched and dropped from the cut list rather than quietly moved, because moving one box breaks the rhythm of all of them. Not one page in this search handles obstacles at all.
How do I calculate the amount of molding I need?
Add up the cut list: four pieces per box, each measured at its long point. The page totals them in linear feet and packs them onto the stock length you pick, so the sticks to cut are counted, not estimated. Spare sticks come on top, from an allowance for spoiled miters: between 10 and 15 % for a wall like this. The trade source we cite refuses a single figure: “5 to 10% for cheap paint grade in large runs and not many miters or very expensive material. 10 to 15% for typical commercial jobs and mid range homes.” It keeps its lower band for runs with not many miters; a wall of boxes, four miters per box, is the opposite case, so we place it in the 10–15 % band. The calculator starts at 10 %, the low end of it.
What this does not do
- One wall at a time, and equal boxes. An intentionally wider center box is a real design and it is not modeled here.
- No corners: inside and outside returns, and how a run meets them, are outside the drawing.
- No cost. We have not sourced US per-foot trim prices we would publish with a date, so there is no dollar figure.
- No fixing schedule: brad length, adhesive and caulk are trade choices, not measurements.
- Each piece is cut whole from one stick; nothing is joined, and offcuts are not re-cut across sticks.
- Fractions display to the nearest 1/16 inch, with full precision kept underneath.