Bridging Distance Calculator (Pre-Failure Check)
Predict if a bridge is likely to sag or fail before running a long print.
Bridge risk
61 / 100
Risk result
High risk61 / 100
- Predicted max bridge25.8 mm
- Requested / max ratio1.08x
- Estimated sag at span0.48 mm
Recommended actions
- Shorten bridge span by reorienting part or adding a support blocker only under the span midpoint.
FAQ
Can this replace bridge calibration prints?
It is a pre-check, not a replacement. Use it to avoid obviously risky spans, then verify with a quick bridge test for your exact printer and filament.
What helps bridges most for PLA and PETG?
Lower bridge flow, moderate bridge speed, and high fan on bridge layers usually give the biggest improvement.
Why does ABS still fail long bridges even with tuning?
ABS stays soft longer and benefits less from high fan, so long unsupported spans sag earlier than PLA under similar geometry.
Related tools & guides
Support Material Estimator
Estimate support grams before slicing when bridges are risky.
Warping Risk Predictor
Check thermal distortion risk for long unsupported spans.
Print Time Estimator
Estimate total job time before slicing.
Free 3D Print Cost Calculator
Full material, electricity, and margin cost breakdown.
How to use the bridging distance calculator
Select your material, nozzle size, bridge speed, flow rate, and fan percentage. The calculator predicts your maximum reliable bridge span and flags failure risk before you commit to a long print.
What is a reliable bridge distance for PLA?
With a well-tuned printer and 100% fan, PLA can reliably bridge 40–60 mm. Beyond 60 mm, sagging becomes likely. Reduce bridge flow to 80–90% and maximise cooling for longer spans.
Why does bridge distance vary by material?
Different materials have different viscosity and cooling behaviour when molten. PLA has low viscosity and cools quickly, making it the easiest to bridge. ABS has high viscosity and poor cooling, limiting reliable bridges to around 25–30 mm without an enclosure.
How can I improve bridge success?
Increase fan speed to 100%, reduce bridge flow rate to 80–90%, lower bridge print speed to 15–25 mm/s, and print at the lower end of your temperature range. These four settings have the biggest combined impact on bridge quality.