The 3am problem
Every maker knows the math anxiety of a 14-hour print and a half-used spool. Slicer says 210g. Spool feels like… some amount. You squeeze it, hold it up to the light, shake it near your ear like a present — and then either gamble the overnight print or waste 40 minutes swapping to a fresh spool you didn't need.
A $10 kitchen scale ends the guessing permanently. Total weight minus empty spool weight equals filament, to the gram. The only knowledge gap is the empty spool weight — and that's a solved problem: this page carries measured weights for 31+ spool types, cross-checked against community weigh-ins and manufacturer specs.
Why grams beat every other method
- Visual estimate: hopeless. The last 20% of a spool looks nearly identical to the last 40% because the coil diameter shrinks toward the hub — the visible layers hold less and less filament.
- Printer tracking (AMS, MMU): counts what was commanded, not what exists — purge towers, failed prints, and manual extrusions drift the estimate; non-ecosystem spools aren't tracked at all.
- Spool windows / markings: a few brands mold percentage marks into the spool. Nice, coarse, and useless for "do I have 218g?"
- The scale: measures reality. Immune to purges, failures, humidity gossip, and marketing. Ten seconds per spool.
Grams → meters → hours
Weight converts to length through density and cross-section. For 1.75mm filament, one gram is:
- PLA (1.24 g/cm³): 0.335 m/g — a full 1kg spool is ~335m
- PETG (1.27 g/cm³): 0.327 m/g
- ABS (1.05 g/cm³): 0.396 m/g — lighter plastic, more meters per kilo
- TPU 95A (1.21 g/cm³): 0.344 m/g
The "print hours" figure uses a typical mid-size-printer consumption of ~24g/h — a planning number, not a promise; a fast CoreXY doing big vase-mode prints can triple it.
Managing a spool shelf like a print farm
Once weighing becomes habit, two upgrades pay off. First, write the remaining grams on masking tape on the spool edge whenever one comes off the printer — future-you trusts the tape. Second, standardize on 2-3 filament brands so a single custom empty-weight measurement covers your whole shelf; the full brand chart lives in our empty spool weights guide when you inherit a mystery spool.
And when the verdict says "not enough" — split the model, or check the Print Time Estimator to see if dropping infill 10% buys the margin. It usually does.
Frequently asked questions
How do I know how much filament is left on a spool?
Weigh the whole spool on a kitchen scale and subtract the empty spool weight. That's it — filament remaining in grams, accurate to a few grams. The only hard part is knowing what the empty spool weighs, which is what this calculator's brand database is for. A Bambu reusable spool is ~216g, a Polymaker cardboard spool ~140g, an eSUN plastic spool ~224-268g depending on production year.
How many meters of filament is 100 grams?
For 1.75mm PLA (density 1.24 g/cm³): about 33.5 meters. PETG is a touch denser so slightly less; ABS is lighter so more — 100g of 1.75mm ABS is about 39.6m. The calculator does the exact conversion for your material.
My scale reads less than the listed empty spool weight. What gives?
Three possibilities: you selected the wrong spool type (cardboard vs plastic of the same brand differ by 100g+), the manufacturer changed spool design between production runs (it happens — weights drift ±10g and occasionally more), or what you have is a refill coil without its spool. Use the custom option and weigh an empty spool of your exact type once — then you know forever.
Can my printer track filament remaining automatically?
Some ecosystems try. Bambu's AMS estimates remaining filament by counting extruded length on RFID-tagged Bambu spools — decent but drifts with purges and failed prints. Prusa's MMU and most Klipper setups don't track weight at all. The kitchen scale method is brand-agnostic and self-correcting: it measures what's actually there, including every purge and failure since you loaded it.
How much filament does a typical print use?
Small desk objects (phone stands, hooks, brackets): 10-50g. Medium functional parts and enclosures: 50-150g. Large helmets, vases, organizers: 200-500g. If you have the STL but haven't sliced yet, our Print Time Estimator reads the file and estimates grams in your browser.
Should I finish a nearly-empty spool or start fresh for a big print?
Run the check in step 3. If the margin is under ~25g, start fresh: end-of-spool filament is the most-humid, most-tangled, tightest-curled part of the coil, and mid-print runout handling (even on printers with sensors) is a seam risk on the part. Save sub-25g remnants for calibration cubes and first-layer tests.
Do empty spool weights really vary between production runs?
Yes — same brand, same product line, different year, different spool. eSUN's plastic spools have shipped anywhere from ~224g to ~268g over the years; several brands quietly moved from plastic to cardboard (lighter) or back. Our database lists ranges and notes where variation is known. For repeat-brand users the fix is permanent: weigh one empty spool, save it as your custom value.