Your lampshade template, ready to print
Calculate a flat cutting pattern for a round tapered or drum lampshade. Enter the top and bottom diameters and the vertical height, then add a glue overlap and separate top and bottom turn-under allowances. Download the template as a full-size SVG or a tiled A4/A3 PDF.
- Free
- No sign-up
- Calculated in your browser
- Includes an assembly plan
For round drum and straight-sided tapered shades. Not suitable for oval, curved or four-sided shapes.
Calculate your lampshade pattern in millimetres
Enter the diameters of the two circular openings and the vertical height. All measurements are in millimetres. The preview updates instantly. Downloads include your selected glue overlap and turn-under allowances.
- Slant height
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- Sector angle
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- Pattern dimensions
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- Top / bottom circumference
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- PDF pages
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Important for cutting: Your selected glue overlap and top/bottom turn-under allowances are included in the solid cutting outline. The dashed grey line marks the original shade contour and the start of the allowances. Material thickness is not compensated automatically. First make a paper test.
Three Measurements, Clearly Defined
Top Diameter
Measure across the centre of the top opening. The calculator assumes a perfect circle.
Bottom Diameter
Measure across the centre of the bottom opening as well. The calculator determines which opening is larger.
Vertical Height
The vertical distance between the planes of the two openings. The tool calculates the slant length.
If both diameters are equal, the pattern is a rectangle. If they differ, it is an annular sector. Measurements refer to the desired cutting surface; rings and material thickness may cause deviations.
Still choosing the shape? Use our lampshade proportions tool before creating the cutting pattern.
How the Pattern Is Calculated
Using the radii R (larger opening) and r (smaller opening), together with the vertical height h, the Pythagorean theorem gives the slant height s. The two arc lengths of the pattern correspond to the circumferences 2πR and 2πr.
Angle α = 360° × (R − r) / s
Outer radius = s × R / (R − r)
Inner radius = s × r / (R − r)
The calculator draws the resulting outline as a vector file. You can continue working with the SVG to scale in suitable software. Larger patterns are divided across A4 or A3 PDF sheets with a 5 mm overlap. The first page is an assembly plan showing the complete sheet layout.
Mathematical basis for the slant height: Wolfram MathWorld, „Conical Frustum“. The angle and radius formulas follow from the arc lengths; derivation and drawing by Designeria. Source checked on 30 September 2026.
Print, Assemble, Cut
The first PDF page shows the assembly plan. Each pattern sheet is labelled, for example A1 or B2. Place A1 in the top left, then arrange letters from left to right and numbers from top to bottom.
Print at 100%
In the print dialogue, select A4 or A3 to match the PDF. Choose “Actual size” and disable “Fit to page”. The calibration line must measure 100 mm.
Cut along the red line
For every sheet except those in the first column, trim the left paper edge along the red dashed line. From the second row down, trim the top edge in the same way.
Align the blue registration marks
Overlap each trimmed sheet by 5 mm with the sheet to its left or above. Align the blue registration marks and outline, then secure the sheets.
Cut the black outline
After assembling the sheets, cut along the solid black line. This is the actual cutting line for the shade.
Make a paper test
Before cutting your final material, check the pattern and selected allowances against the existing rings.
Privacy: Measurements are calculated in your browser only. They are not sent to another service to create the PDF or SVG.
Example: a tapered lampshade with a 180 mm top and 300 mm bottom
With a vertical height of 220 mm, these values describe the shade before any allowances. Select “Tapered example” in the calculator to load the same dimensions with all allowances set to 0 mm.
| Measurement | Value |
|---|---|
| Top diameter | 180 mm |
| Bottom diameter | 300 mm |
| Vertical height | 220 mm |
| Slant height | 228.0 mm |
| Sector angle | 94.7° |
| Inner / outer pattern radius | 342.1 / 570.1 mm |
| Top / bottom circumference | 565.5 / 942.5 mm |
Calculation: s = √(220² + 60²) ≈ 228.0 mm. The sector angle is 360° × 60 / s ≈ 94.7°. If both diameters are 200 mm instead, a 220 mm tall drum shade unfolds into a rectangle approximately 628.3 × 220 mm before allowances.
Lampshade templates: questions about calculation, cutting and printing
Is the lampshade template calculator completely free?
Yes. The calculation, preview and SVG or A4/A3 PDF downloads are free and require no sign-up. Your dimensions and template generation stay in your browser.
Which lampshade shapes does it support?
Round, straight-sided drum and tapered lampshades. Equal diameters produce a rectangle; different diameters produce an annular sector. The top opening can also be larger than the bottom. Oval, curved, multi-sided and pleated shades are not supported.
Should I enter the vertical height or the sloping side length?
Enter the vertical distance between the two opening planes. The calculator works out the slant height, also known as the true side length. Entering the sloping length as the height would produce an oversized pattern for a tapered shade.
How do I add a glue seam and turn-under allowances?
Enter the glue overlap and separate top and bottom turn-under allowances in millimetres. A glue tab is added to one side only; the turn-under allowances follow the two edges. Set a value to 0 mm to disable it. Choose allowances to suit your material, rings and making method; there is no single correct value for every shade.
How do I print the template at actual size?
Select A4 or A3 and print the PDF using “Actual size” or 100%. Disable “Fit to page”. Check that the calibration line measures 100 mm. The assembly plan shows where each numbered sheet belongs. Cut the solid black outline only after assembling the sheets.
What is the difference between SVG and PDF?
The SVG contains the vector outline with dimensions in millimetres for suitable drawing or cutting software. The PDF is prepared for A4 or A3 printing, with an assembly plan, numbered pattern sheets and registration marks. When importing the SVG, make sure your software preserves its millimetre dimensions.
Why is a tapered lampshade pattern curved instead of trapezoidal?
When the surface is unrolled, the circular openings become circular arcs. A truncated cone therefore forms an annular sector with curved edges. A straight trapezoid does not geometrically match the circular openings.
What are the calculator’s limits?
Diameters and vertical height must be between 20 and 1,000 mm; each allowance between 0 and 100 mm. PDFs are limited to 40 pattern sheets plus one assembly plan. Larger print grids disable the PDF; SVG remains available for valid geometry. Overlapping or excessive allowances are rejected. Material thickness, stretch and the fit of your specific rings are not compensated automatically.