Browser-only OrcaSlicer multi-material tool

Filament Flush Waste Calculator

Every colour change on an AMS or MMU print pushes filament through the nozzle to clear the old colour. This calculator turns the flush volume you set in the slicer and the number of changes in the print into grams, metres and money, and shows what share of the print's filament that purge consumes. Add the prime tower's footprint and height if you want it in the total. Every figure comes from your own slicer settings — the page does not recommend a flush volume.

1 — Flush volume and changes

Take all four figures from the slicer. The flush volume is the one you set per change, and the change count is the number of tool changes or M600 events in this print.

Count the colour or material switches in the preview, or count the M600 commands in the G-code. Every switch is one flush event, even when both colours are loaded in the same AMS.

OrcaSlicer's multi-material settings hold the flush volume for each filament pair. Use the value you actually set; 90–120 mm³ is a common starting point for PLA, not a recommendation for every material or colour pair.

PLA is about 1.24, PETG 1.27, ABS 1.04, ASA 1.07, TPU 1.21 and polycarbonate about 1.20 g/cm³. Use the spool's data sheet when it is available.

Used only to convert the purged volume into a filament length. Most desktop printers use 1.75 mm; some older machines use 2.85 mm.

2 — Print context and prime tower

The part's own filament use gives the waste a denominator. The tower fields are optional — leave them at zero for a print without a prime tower.

The part's filament weight from the slicer summary. Do not add the flush or tower here — the calculator adds them itself when it reports the whole print.

In your own currency. The page never converts or labels a currency, so keep every money figure in the same one.

Width times depth of the tower's base. The slicer preview or the prime-tower settings show both dimensions.

The tower's printed height for this job, not the maximum the slicer allows.

100% treats the tower as a solid block, which is a geometric upper bound. Lower it to match the sparse material the slicer actually prints if you know that proportion.

Enter the flush volume per change and the number of filament changes, then the part's filament weight and your filament price. The estimate appears here as you type. Nothing you enter leaves this page.

How the flush waste is calculated

The estimate follows the order the slicer works in. The volume of filament pushed through the nozzle is a volume, so it becomes a weight only after the material density is applied.

  1. Flush volume. The number of filament changes multiplied by the flush volume set per change:flush (mm³) = changes × volume per change.
  2. Weight. Cubic millimetres become cubic centimetres, then grams at the material density:grams = (mm³ / 1000) × density. PLA at 1.24 g/cm³ turns 14,400 mm³ of purge into 17.86 g.
  3. Length. The same volume divided by the filament's cross-section gives the metres consumed:area = π × (diameter / 2)², thenlength = volume / area. This is the number that makes a purge easy to picture against a spool.
  4. Prime tower. Footprint multiplied by height, then by the material fraction:tower (mm³) = footprint × height × fraction. At 100% this is the solid envelope, not a measured tower weight.
  5. Share and cost. Waste is compared with the part's own filament and with the whole print, then priced at your price per kilogram:waste cost = (grams / 1000) × price per kg.

The page never suggests a flush volume. Flush volume is a slicer setting that depends on the two materials, the colour difference, the nozzle and the purge speed, so the estimate is only as good as the volume and change count you enter.

Worked example

The page opens with 120 filament changes at 120 mm³ each, PLA at 1.24 g/cm³, a 1.75 mm filament, 180 g in the part and a price of 25 per kilogram. The flush volume is 14,400 mm³, which is 14.4 cm³ and17.86 g of purge waste. That is about 5.99 m of filament and 0.15 g per change.

  • All filament in the print: 180 + 17.86 = 197.86 g
  • Waste as a share of the part: 9.9%
  • Waste as a share of all filament: 9.0%
  • Waste cost at 25 per kg: 0.45, or 9.0% of the filament bill

Add a 900 mm² footprint at 60 mm high with the tower at 100%, and the envelope is 54,000 mm³ — another 66.96 g. That is why the fill fraction matters: the real tower is not a solid block, and a 30% figure would put the same tower at about 20.09 g.

Reading the result honestly

  • Flush is not always spent. Wipe-into-infill, wipe-into-support and per-pair flush calibration can move some of the purge into useful material. This estimate uses the volume you typed; it does not know whether those options are enabled.
  • One volume fits all in this estimate. Real slicers store a different flush volume for each filament pair. If the print changes between light and dark colours, the average per change is rarely the same as the darkest pair's value. A single representative volume is still useful for a first estimate, but the slicer's flush table is the authority.
  • The tower figure is a shape, not a weight. Footprint times height measures the space the tower occupies. The slicer's preview reports the actual tower filament; lower the material fraction until the estimate matches it if you want a closer number.
  • The purged material may cost more. The calculation prices every gram at one price per kilogram. If the flushed material is a different or more expensive filament, the true waste cost is higher than the share shown here.

Frequently asked questions

Does this calculator choose a flush volume for me?

No. It multiplies the volume you set in the slicer by the number of changes. Flush volume depends on the material pair, the colour difference, the nozzle and the purge speed, so a generic recommendation would be worse than the value already in your profile.

How do I count filament changes?

Count the tool changes in the slicer preview, or count M600 commands in the G-code. A change between two colours is one event even when both spools are loaded in the same AMS or MMU. If you only know the total flush volume, divide it by the volume per change to get an approximate event count.

Why is the waste a different percentage of the part and of the print?

The two denominators are different. Waste divided by the part's filament answers "how much extra material does the flush add?" Waste divided by the part plus the waste answers "what share of the filament I load is thrown away?" Both are shown because both are useful, and neither is wrong.

Should the prime tower be included?

Include it when the print actually has one. A prime tower is printed material that is not part of the model, so it belongs in the waste figure even though it is a different mechanism from the colour-change purge. If the print uses no tower, leave the footprint and height at zero.

Does the estimate work for a single-colour print?

Yes, but the flush figure will normally be zero because there are no changes. Set the change count to zero and enter a tower if one is printed; the page then reports the tower volume on its own.

Is anything I type sent anywhere?

No. The arithmetic runs in this page. No value is uploaded, written to storage, added to the URL or logged.

Related reading and tools

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