Filament Spool Remaining Calculator
Determine exactly how much material is left on your open spool, estimate remaining prints, and evaluate your filament inventory value instantly.
Understanding Spool Weights
Effective 3D printing material management relies on knowing exactly how much filament is left on an open spool before starting a long print. The most accurate way to check your filament inventory is by weight.
Total Spool Weight (Gross)
This is the number you see when you place your current, partially-used spool on a digital scale. It includes both the plastic filament and the physical reel holding it.
Net Filament Weight
This is strictly the weight of the usable plastic (commonly 1000g or 1kg for a standard PLA spool or PETG spool). This does not include the weight of the cardboard or plastic reel.
To find the grams remaining, you simply weigh the open spool and subtract the empty spool weight. Length estimates depend entirely on material density (g/cm³) and filament diameter. Support for both 1.75 mm and 2.85 mm filament is included in this tool to ensure accurate filament length calculations.
Worked Example
Let's say you have a partially used 1kg PLA spool that cost $22.00, and you want to know if you can print a model that your slicer says requires 250g.
- Step 1: You place the spool on a kitchen scale. The Total Spool Weight reads 580g.
- Step 2: You look at the manufacturer's sticker, and the Empty Spool Weight is listed as 220g.
- Step 3: Remaining Filament = 580g - 220g = 360g.
- Step 4: The slicer requires 250g. Since 360g > 250g, you have enough material to safely start the print.
- Step 5: Cost per gram = $22.00 / 1000g = $0.022 per gram. The remaining 360g holds a material value of $7.92.