**Required tools**: top quality caliper (error 0.01 mm)

- Unroll at least five (5) meters of filament before taking any measurements.
- Take measurements of four (4) points separated by two (2) meters each.
- Take two (2) measurements at each point using the tip of the caliper.

2nd measurement needs to be taken at a 90° angle from the previous measurement to avoid inaccurate readings from out-of-round filaments.

1st measurement 2nd measurement - Add both values together and divide by 2 to get the average diameter of each point.
- Now add all average diameter values together and divide by the number of samples (4 in this case) and then subtract the spool diameter (1.75mm) and you'll have the tolerance accuracy.

### Example:

#### Taking measurements:

Point | 1st measurement | 2nd measurement |

0m | 1.71 | 1.75 |

2m | 1.72 | 1.74 |

4m | 1.75 | 1.69 |

6m | 1.72 | 1.76 |

#### Calculating average diameter per point:

**0m:** 1.71 + 1.75 / 2 = 1.73

**2m:** 1.72 + 1.74 / 2 = 1.73

**4m:** 1.75 + 1.69 / 2 = 1.72

**6m:** 1.72 + 1.76 / 2 = 1.74

#### Calculating spool average diameter:

(1.73 + 1.73 + 1.72 + 1.74) / 2 = 1.73

#### Calucalting tolerance accuracy:

1.73 - 1.75 = -0.02