Use the whole plate, not just the finished part
Start with the net filament available: a full 1 kg supply is 1,000 g of material. When weighing a used spool, subtract its actual empty-spool weight. Do not count packaging or assume every spool has the same tare weight.
Slice the planned plate and use its total material requirement, including supports and any brim, purge or tower. If the slicer already includes these in a total, do not add them a second time. A 20 g finished object does not by itself establish that a 1 kg spool can make 50 copies.
Calculate complete plates first
Usable grams = net filament remaining minus your chosen reserve. Full plates = usable grams divided by grams per plate, rounded down. Planned parts = full plates multiplied by parts per plate.
A reserve is a budgeting choice, not a measured reliability guarantee. Choose it for your own weighing uncertainty and additional material use. The calculator does not estimate the probability of a successful print.
Compare the same five-part batch at different material totals
Keeping the example's 950 g usable supply and $20/kg price, a 125 g plate gives 7 complete plates and 35 planned parts, at $0.50 material cost each. A 150 g plate gives 6 complete plates and 30 planned parts, at $0.60 each.
These are checked arithmetic examples, not physical test prints or typical performance claims. Compare your own separately sliced layouts before choosing settings.
Do not count an unsliced final partial plate
In the 125 g example, 75 g remains after seven full plates, in addition to the reserve. That does not automatically mean three extra parts. A smaller final plate may have a different share of supports, purge or tower material. Slice it separately before planning extra copies.
For multicolor jobs, each color can be a separate bottleneck. Adding 100 g of one color to 900 g of another does not mean either color can supply a 1,000 g job. Compare each spool's available grams with the amount of that color needed per plate.
Turn material cost into a full quote
Material cost per part is total plate grams divided by part count, multiplied by the price per gram. It excludes electricity, machine wear, preparation, finishing, packaging and retries. Use the full cost calculator for those items, then use Price & margin for order shipping, selling fees and your target margin.
Keep the production plan separate from the customer promise. Failed plates, queues and delivery time are not covered by the spool budget. The estimator runs in your browser and does not upload model files or your input values.