Measure the shape you actually want

For a doorway, measure across the outside trim and enter each side as an end hang. A 3-foot-wide door with 7-foot sides needs 17 feet for a straight, single layer before joins or spare length. For a mantel, measure between fixing points, then choose the number of swags and how far each dips. End hangs are extra.

If you’ve already draped string into the shape you like, use Measured string route and enter its full length. Leave end hangs at zero if your string includes them. This mode doesn’t add more length for swags. It also works for an uneven banister or a wrapped route that the level-swag model can’t describe.

The Ballard Designs measurement guide separates door width from its two sides and suggests measuring a string laid out in your chosen shape. Its 1.5-times mantel rule is a styling shortcut. This planner instead lets you choose the drop.

How the estimate works

Each swag is an equal-width, symmetrical parabola between level fixing points. If the total span is W, the number of swags is N and the drop is d, one swag spans s = W/N. With r = 4d/s, its length is s/2 × (√(1+r²) + asinh(r)/r). At zero drop, its length is s. This comes from the OpenStax arc-length integral ; the parabolic shape is our modeling assumption.

The route is the swags plus both end hangs. Spare length is added to each layer. Doubling makes two complete layers of that route; it doesn’t increase the drop or predict how full a particular product will look.

Whole strands are allocated separately to each layer, with your chosen overlap at every join. For k strands of length L and overlap o, usable coverage is kL − (k−1)o. We choose the smallest whole k that covers the layer, then round up to whole packs. We don’t assume you can cut strands or reuse a short offcut in another layer. Check the packaging for strand length, pack quantity and whether physical joining is permitted.

Excess in used strands is length beyond your planned route and spare, after join overlap. It may stay attached or need hiding; it isn’t necessarily a reusable offcut. Unused whole strands come from rounding to a pack. Neither amount is a promise of usable material after installation.

Check the drape before buying

Garland stiffness, fullness and fixing points can change the result. Vickerman’s calculator guidance also calls its drape estimate approximate and says it doesn’t determine electrical run limits. Our model has been checked mathematically and in browser tests, but hasn’t been validated with physical garland. Lay out string first if the fit is tight. Use the product’s own instructions for lighting connections, cutting and installation.

For a small room, start with one garland placement that leaves the room usable . If the length fits but the arrangement still looks awkward, check garland styling mistakes before adding another layer.

Sources reviewed October 1, 2026. Strand sizes in the examples are planning inputs, not product recommendations or a live catalog.