Guide
How much filament is left in your AMS?
The AMS doesn't put your spool on a scale. It works the number out. Here's how, how far to trust it, and how to see the grams for every spool at a glance.
In short
The AMS estimates what's left; it doesn't weigh the spool.
- Bambu Lab spools with an RFID tag: the tag gives the spool's net weight (for example 1,000 g), and the AMS reports the share remaining as it feeds. Multiply the two: 81% of a 1,000 g spool ≈ 810 g.
- Third-party spools, or no tag: the printer doesn't know the starting weight, so there's no remaining amount to show.
Bambu Bar does the maths for you and shows the grams left on every Bambu Lab spool, in the Mac menu bar or the Windows tray, on its Filament page and in the large desktop widget.
Where the number comes from
Two numbers make the grams:
- The spool's net weight, read from its Bambu Lab RFID tag: 1,000 g for a standard spool.
- The share remaining, which the AMS estimates as it feeds filament and reports as a percentage.
Multiply them and you have an approximate weight: 81% of a 1,000 g spool is about 810 g.
Bambu Lab spools vs third-party spools
| Spool | Name shown | Amount shown |
|---|---|---|
| Bambu Lab, with RFID | The colour's real name: Jade White, Charcoal, Grass Green | Grams left |
| Third-party, or no tag | The maker and product of the slot's preset, like SUNLU PLA Matte | No amount |
| Empty slot | Empty |
Without a Bambu Lab RFID tag, the printer has no way to know how much was on the spool to begin with, so there's nothing to estimate from. Set the slot's filament preset on the printer or in Bambu Studio, so at least its name appears instead of a generic "PLA".
How accurate is it?
Good enough to plan with, not good enough to bet a 12-hour print on. The AMS estimates what's left from what it has fed, so small errors add up over a spool's life. Treat the grams as a guide, and leave a margin on long prints.
Will it last this print?
Compare two numbers:
- The grams left on the spool (Bambu Bar shows them; the tooltip shows both, like 81% · ≈ 810 g).
- The filament the plate needs, which Bambu Studio shows when you slice.
If the spool has comfortably more than the plate needs, you're fine. If it's close, swap in a fuller spool before you start.
By AMS model
Bambu Bar shows spools and grams on every AMS: the AMS, AMS 2 Pro, AMS HT, AMS Lite and the H3C's AMS 3H. Where the AMS reports them, it also shows each unit's humidity and temperature. The AMS Lite on the A1 and A1 mini has no humidity sensor, so those printers show spools and grams without humidity.
Seeing it on your Mac or PC
Bambu Bar puts your filament where you'll actually look:
- The menu bar or tray panel: the spools in your AMS, with the one feeding right now.
- The Filament page: every unit and spool, the external spool, and the total grams on hand across all your Bambu Lab spools.
- The large desktop widget: every AMS spool with grams left, on your desktop.
It works with every supported printer, on your local network, with no Bambu Lab sign-in. It's free to use, on macOS 26 or later and on Windows 10 and 11. More in AMS filament. Get Bambu Bar · Bambu Bar for Windows
Questions, answered
How does the Bambu Lab AMS know how much filament is left?
It doesn't weigh the spool. On Bambu Lab spools, the RFID tag gives the spool's net weight, and the AMS estimates the share remaining as it feeds filament. Multiplying the two gives an approximate weight: 81% of a 1,000 g spool is about 810 g.
Why doesn't my third-party spool show how much filament is left?
Without a Bambu Lab RFID tag, the printer doesn't know the spool's starting weight, so it can't show a remaining amount. Apps like Bambu Bar then show the slot's material and preset name, such as SUNLU PLA Matte, but no grams.
How accurate is the AMS remaining filament?
It's an estimate, not a measurement. Use it to plan, and leave a margin on long prints.
How can I see AMS filament in grams on a Mac or PC?
Bambu Bar shows each AMS slot with its colour name and, on Bambu Lab spools, the grams left: in the Mac menu bar or Windows tray panel, on its Filament page (with the total on hand) and in the large desktop widget.
Read next
- AMS filament and grams leftHow much filament is left on each AMS spool, in grams, with colour names and humidity, and where the numbers come from.
- Desktop widgetsSmall, medium and large widgets for the Mac or Windows desktop with your print's progress, time left, temperatures and filament, one per printer if you like.
- Several printers at onceEvery printer on one Mac or PC: the ones that need you first, then the rest by time left, with widgets and alerts for each.
- Compatible Bambu Lab Printers: All 15 ModelsBambu Bar works with all 15 Bambu Lab printers: P2S, P1S, P1P, X1 Carbon, X1, X1E, X2D, A1, A1 mini, A2L, H2D, H2D Pro, H2C, H2S, H3C. Compare camera setup, chamber data and AMS filament for yours.
Stop walking to the printer
Track Bambu Lab print progress, time left, temperatures, AMS filament and the live camera on your Mac. Get print alerts and desktop widgets without opening Bambu Studio.
Print progress, alerts and filamentmacOS 26+, Apple silicon & Intel Also on Windows · Linux coming next
Stop walking to the printer
Track Bambu Lab print progress, time left, temperatures, AMS filament and the live camera on your PC. Get Windows notifications and desktop widgets without opening Bambu Studio.
Print progress, alerts and filamentWindows 10 and 11, x64 & ARM64 Also on the Mac · Linux coming next