3D Printing Calculators
Remaining Filament Estimator
https://www.3dsizing.com/calculators/remaining-filament/
Estimate only — not firmware, a slicer profile or a shop quote. Confirm on a test print.
Remaining Filament Estimator
The box said 1 kg, the scale says 600 g, and the empty spool is not free. Subtract tare, then turn leftover plastic into metres using the same cylinder density as the length-to-weight tool.
Inputs
Results
- Remaining plastic
- 420.0g
- Remaining length
- 140.8m
- Of a 1 kg net spool
- 42.0%
Capped at 100%. A 2 kg spool can read 100% while still holding more than a kilogram.
Recommended gear
0.01 g scale
Spool tare only works if the scale is honest. Weigh the same way every time.
Typical range: $10–$25
Empty filament spool
Keep one empty of the same brand so tare is a measurement, not a forum guess.
Typical range: $5–$15
PLA 1 kg spool
Net plastic is 1 kg; the cardboard or plastic hub is extra mass on the scale.
Typical range: $15–$30
Calculation method
Remaining mass is current spool weight minus empty-spool tare. If that leftover is not positive the result is invalid. Length in metres treats the filament as a cylinder: grams per metre = π × (diameter_mm / 2)² × density g/cm³, then remaining metres = remaining grams / grams per metre. The percentage is remaining grams over 1000 g, capped at 100%, i.e. a nominal 1 kg net spool. Densities match the length-to-weight converter (PLA 1.24, PETG 1.27, ABS 1.04, TPU 1.21, nylon 1.14, ASA 1.07).
Exact formula
remaining_g = current_g − empty_spool_g. Metres from remaining mass as a cylinder: g/m = π (d_mm/2)² × density. remaining_% = min(100, remaining_g / 1000 × 100) assuming a 1 kg net spool. Limits: Percent assumes a 1 kg net spool and is capped at 100%. Metres use the same neat-polymer cylinder as length-to-weight.
Write tare on the spool
A Sharpie on the hub beats guessing next month. Some vendors print tare; many do not.
Slicer remaining filament
Firmware length estimates assume perfect e-steps and density. A scale plus this converter is usually closer after a few colour changes.
Frequently asked questions
Why is remaining percent against 1 kg?
Most desktop spools are sold as 1 kg of plastic. If you buy 2 kg or 250 g refills, ignore the percentage and use grams or metres.
My empty spool is 220 g, not 180.
Change the tare. Cardboard, refill rings and branded plastic hubs are all over the map. Weigh an empty of the same SKU.
Can I finish a 50 g print?
If remaining grams are above 50 g plus purge, yes on paper. AMS flush, failed first layers and a wet hygroscopic roll still eat margin.
Does diameter change the grams?
Grams come from the scale. Diameter only converts those grams into metres. 2.85 mm has more mass per metre, so fewer metres for the same leftover.
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