Calculator
Cone & Cylinder Flat Pattern Calculator
The flat blank for a rolled cone or cylinder, laid out on the plate’s mean diameter: radii, sector angle, blank size and weight, with a DXF you can send to the cutting table.
How the flat pattern is figured
The pattern is laid out on the mean diameter: outside diameter minus one plate thickness, or inside diameter plus one. With R and r the mean radii of the large and small ends and H the height:
s = √(H² + (R − r)²)
outer radius = s × R ÷ (R − r)
inner radius = outer radius − s
sector angle = 360° × R ÷ outer radius
cylinder blank = π × mean diameter × height
Example: a cone 48 in. OD at the large end, 24 in. OD at the small end and 24 in. tall in 3/8 in. plate has mean radii of 23.81 and 11.81 in., a slant height of 26.83 in., an outer radius of 53.25 in., an inner radius of 26.41 in. and a sector angle of about 161°.
Weight comes from the mean surface (π × (R + r) × s) times the thickness and density. Allow extra material for the seam weld prep and for trim when you nest the blank.
Questions
Should I lay out a cone on the inside, outside or mean diameter?
Lay the blank out on the mean diameter, the middle of the plate thickness, because that line neither stretches nor compresses as the plate rolls. Enter the size from your drawing, say whether it is the inside or outside, and the calculator works from the mean.
How do you calculate a cone flat pattern?
From the mean radii of the large end (R) and small end (r) and the height H: slant height s = √(H² + (R − r)²), outer radius = s × R ÷ (R − r), inner radius = outer radius − s, and sector angle = 360° × R ÷ outer radius.
Can you roll the cone or cylinder for me?
Yes. We roll cylinders, cones, half-shells and segments up to 16 ft in diameter and up to ¾ in. thick, depending on width and grade, and we can cut the blanks by laser, plasma or oxy-fuel. Send the drawing or the DXF from this page.
What does the DXF contain?
The flat pattern at full size in inches: for a cone, two concentric arcs and the two straight edges; for a cylinder, the rectangle. Add your own allowance for the seam weld prep and trim before nesting.
Request a quote
Send us the drawing, or the cut list.
We take DXF, DWG and STEP files, dimensioned PDFs and bills of material. Our estimating team reviews every request and comes back with an itemized quote.
- DXF
- DWG
- STEP
- XLS/CSV