3DPrintCalcs
Bridge Calculator — Maximum Bridging Distance
Determine the maximum bridging distance for your printer and material settings.
How We Calculate This
Bridge Calculation
- Max bridge = Material base x Cooling factor x Speed factor x Nozzle factor
- Sag estimate = Length² x Material factor / (Cooling x Nozzle factor)
- Bridge time = Bridge length / Print speed
The material base is a conservative, printer-dependent starting estimate (PLA ~50mm, PETG ~40mm, ABS ~25mm with a 0.4mm nozzle). Full cooling (fan factor 1.0) and a slow 15-25 mm/s speed extend the achievable span; a wider 0.6-0.8mm nozzle helps further by laying a stiffer strand. The sag estimate is a rough indicator, not a calibrated physics model — sag grows with the square of the span, so doubling the bridge length roughly quadruples the sag, while strong cooling and a thicker strand reduce it.
Frequently Asked Questions
Bridging is when the printer extrudes filament across open air between two support points, like a bridge. The filament is pulled taut between the two sides, relying on tension and rapid cooling to hold shape.
Bridging speed should typically be 15-25 mm/s. Slower speeds allow more cooling but may cause blobs at the start. Faster speeds stretch the filament more but keep it taut. Most slicers have a dedicated bridge speed setting.
Short bridges (under 20mm) typically have less than 0.5mm sag with PLA and good cooling. Longer bridges sag more — a 50mm bridge might sag 1-2mm. Sag increases roughly with the square of the bridge length.
Fan speed is critical for bridging. Maximum cooling (100% fan) helps solidify the filament before it sags. PLA bridges well at 100% fan, while ABS bridges poorly because it needs low fan speed to avoid cracking.
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Last updated: February 2026
All calculations are estimates. Always verify settings with test prints before committing to final prints.