The formula for calculating how much moulding you need for a picture frame — and why the real problem starts when you have more than one order.
Every picture frame has four cuts — two for the width and two for the height. Each cut needs to account for the artwork size, the moulding width on both sides, and a small allowance so the frame opening isn't too tight. Here's the formula for each cut:
Cut Length Formula
cut length = artwork dimension + (2 × moulding width) + allowance
A standard frame uses two width cuts and two height cuts. Total moulding needed is the sum of all four cuts. If you're cutting from the same stick, add kerf (typically 0.125") between each cut for the material removed by the saw blade.
Say you're framing a 16" × 20" piece of artwork with a moulding that's 1.5" wide. Using a standard allowance of 0.125" per side:
That's 7 feet and three quarters of an inch. From a standard 120" (10-foot) stick, you'd have about 35" of leftover — a remnant you could use for a smaller frame later, or waste if it sits on the rack too long.
Kerf is the width of material removed by each saw blade pass. A standard miter saw blade has a kerf of about 0.125" (1/8"). It doesn't sound like much, but across a full day of cutting, kerf adds up. A busy shop making 40 cuts a day loses 5 inches just to saw blades. Over a month, that's 12+ feet of moulding turned to dust. Account for kerf in every cut plan or you'll end up short on stock partway through a batch.
Allowance is the extra space added to each cut so the frame opening is slightly larger than the artwork and glass package. A typical allowance is 0.125" (1/8") per cut. Some shops use 1/16" for tighter fits on small frames. This gets set once in your workflow and shouldn't change job-to-job.
The moulding width is added to both sides of every cut to produce the full outside dimension of the frame. A narrow moulding (0.75") adds 1.5" total per cut. A chunky gallery moulding (3") adds 6" per cut. This is usually pulled from your moulding profile or catalog — you shouldn't have to enter it every time.
Calculate moulding needed for a single frame. For multiple orders on the same profile, you need an optimizer.
The formula above works fine for a single frame. But a real shop doesn't cut one frame at a time. You've got a stack of work orders, multiple profiles, remnants on the rack from yesterday, and fresh sticks in stock. The problem isn't the math for one frame — it's figuring out how to arrange 15 orders across as few sticks as possible without wasting material.
That's an arrangement problem, and it's what your brain is doing (slowly, imperfectly) every time you eyeball a cut list and try to figure out what fits where. The variables compound fast:
By the time you're arranging 30+ cuts across multiple sticks with remnants in play, the number of possible layouts is more than anyone can sort through by hand in the time you actually have between jobs. That's not a spreadsheet problem. That's an optimizer problem.
Miter cuts are standard in picture framing — they're already factored into the formula above. Each cut is measured at the long point of the miter (the outside edge), so the formula gives you the longest dimension of each piece. The moulding width added to both sides accounts for the 45-degree angle at each corner.
Rabbet measurements refer to the inside edge of the frame — where the glass sits. Point-to-point measurements refer to the full outside dimension. The formula above produces rabbet-to-rabbet dimensions by default (artwork + moulding on both sides). If your saw is set up for point-to-point, you'd measure differently. RailChop supports both — you set your shop's standard once in settings.
A small safety margin is reasonable for high-value moulding, but adding arbitrary extra length to every cut is how waste compounds. The better approach is to get the math right in the first place (the formula above, with accurate kerf and allowance), track your remnants so nothing gets lost on the rack, and batch orders by profile so cuts from different frames share sticks efficiently. That way you're preventing waste rather than padding it.
Industry averages for moulding waste range from 15% to 25%, depending on frame sizes and how orders are batched. Shops that cut one order at a time from fresh sticks tend toward the high end. Shops that batch orders by profile, use remnants, and optimize their cut layouts can get below 15%. The biggest single improvement most shops can make is batching — cutting multiple orders from the same profile together rather than one at a time.
RailChop does this for every order, every stick, every day — in under a second, right at the saw.
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