What is bridging in 3D printing?

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.

What speed should I print bridges at?

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.

How much sag is normal for bridges?

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.

Does fan speed matter for bridging?

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.

3DPrintCalcs

Bridge Calculator — Maximum Bridging Distance

Determine the maximum bridging distance for your printer and material settings.

Bridge Length

Unsupported span distance

Nozzle Diameter

Bridge Speed

Cooling Fan

Material

How We Calculate This

Bridge Calculation

Max bridge = Material base x Cooling factor x Speed factor
Sag estimate = Length² x Material factor / Cooling
Bridge time = Bridge length / Print speed

Sag increases with the square of the bridge length, so doubling the bridge distance quadruples the sag. Good cooling and appropriate speed can significantly improve bridging performance.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.