Window screen calculator for rescreening frames or fitting fly screens

How the calculator works out the screen

The screen you need is the sum of the pieces you cut, one per window, each the size of the frame plus a margin on every side, laid out on the roll or kit sold in the store. The calculator adds 1 in per side (2 cm in metric). Phifer's instructions overlap the screen 1/2 in on all sides of a window frame and allow 2-3 in per side on large patio panels; the extra gives you something to hold while you pull the screen tight, and you trim it off once the spline is in. You can change the margin in the advanced options.

Pieces go on the roll in rows, like a cutting layout: each row is as long as its longest piece, and two pieces sit side by side when the roll is wide enough. Fiberglass screen has the same weave both ways, so a piece can be turned: the calculator tries both directions and keeps the layout with fewer rolls, then the one with less screen unrolled. A piece bigger than the roll (or kit) both ways cannot be cut in one piece, and the calculator tells you which one it is.

Spline, or hook-and-loop tape, is the perimeter of each frame: 2 × (width + height), times the number of identical windows. Spline is pressed into the groove all around the frame; tape goes on the four inner sides of the window frame, as tesa shows for its fly screens. Kits already hold the spline or tape. With a roll, the calculator counts 25 ft rolls of spline (Phifer's shorter length) or 15 ft rolls of tape (VELCRO Brand Sticky Back).

Worked example: rescreening three windows with spline

These are the values the calculator opens with in US units: three window screens 34 × 54 in, frame and spline, a 48 in × 25 ft roll and 1 in of margin.

• Each piece is 36 × 56 in
• 56 in does not fit across a 48 in roll, so each piece runs 36 in across and 56 in along the roll
• Screen: 3 × 56 = 168 in, or 14 ft of the 25 ft roll
• Spline: 2 × (34 + 54) × 3 = 528 in = 44 ft, so 2 rolls of 25 ft

You buy 1 roll of 48 in × 25 ft screen, 2 rolls of 25 ft spline and a spline roller. If you fit the screen to the window frames with hook-and-loop tape instead, the same 44 ft takes 3 rolls of 15 ft. With Phifer's 36 × 84 in kits each piece fits exactly across the kit, one per kit: 3 kits.

In metric (UK), the calculator opens with two windows 1.00 × 1.20 m and a patio door 0.80 × 2.20 m on a 120 × 250 cm refill roll. The door takes the first roll (2.24 m), the two windows the second (1.24 + 1.24 = 2.48 m): 2 rolls, 4.72 m unrolled, and 14.80 m of Velcro, which is 3 rolls of 5.6 m.

Typical screen sizes: cut size and spline

With 1 in of margin per side:

Screen	Cut size	Spline	36 × 84 in kit
24 × 36 in	26 × 38 in	10 ft	fits
30 × 48 in	32 × 50 in	13 ft	fits
34 × 54 in	36 × 56 in	14 ft 8 in	fits exactly
36 × 80 in door	38 × 82 in	19 ft 4 in	too wide

A screen door 36 in wide needs a 48 in roll: the cut piece is 38 in on its short side. In metres, a 1.20 × 1.40 m window fits a 130 × 150 cm kit but not a 120 cm roll.

Screen rolls, kits, spline and tape you can buy

Phifer makes fiberglass rolls from 16 to 96 in wide and from 84 in to 100 ft long, and sells a kit with a 36 × 84 in roll, spline and a roller. A long roll is worth it for several windows, because a piece cannot straddle two short rolls. Type the width and length of the roll you find in the store into the calculator. In the UK and Europe, tesa sells 130 × 150 cm window kits with the tape included, a 120 × 250 cm fibreglass refill roll and the tape on its own in 560 cm rolls.

Measure a screen frame from the outer edge of the spline groove on one side to the other. For tape, measure the window frame where the tape will go. Spline comes in diameters from .125 to .250 in: measure the width of the groove or take a piece of the old spline to the store.

Common mistakes

• Cutting the screen to the exact frame size. With no margin you cannot pull it tight, and the edges slip out of the groove. Trim after the spline is in.
• Adding short rolls together. Every piece has to come out of one roll: two 7 ft rolls do not make an 8 ft piece.
• Always cutting pieces upright. A screen 43 in wide and 12 in tall, turned across a 48 in roll, uses 14 in of screen instead of 45 in.
• Using a window kit for a screen door. A 36 × 84 in kit is too narrow for a 36 in door once you add the margin.
• Guessing the spline size. Spline that is too thin pops out of the groove; spline that is too thick will not go in.