Measure actual filament diameter

Slicers assume 1.75 mm. Real filament runs 1.70–1.78, and that difference is a direct multiplier on every extrusion the printer makes.

Phase 1 — Extrusion accuracyabout 5 minper filament

How to do it

1. Take caliper readings at five points along a metre of filament, rotating 90° between each.
2. Average them.
3. Enter that number as the filament diameter in your slicer.
4. Rotating between readings matters: filament is rarely perfectly round, and measuring the same axis five times hides the ovality you are trying to average out.

How to read the result

An averaged diameter you enter into the slicer, replacing the nominal 1.75.

What you need

• Digital calipers reading to 0.01 mm. Any inexpensive pair will do — you are comparing measurements, not certifying them, so absolute accuracy matters far less than reading consistently.
• About a metre of the filament you intend to print with.

Redoing this invalidates

Calibration is a chain. Change this and the results below were measured against the old value:

• Calibrate flow ratio / extrusion multiplier

Open First Layer →
The app walks this in order, generates the test model for your nozzle and filament, and records what you measure so nothing has to be repeated. Free, no account, works offline.