Costing a Print When the Slicer Counts Grams and the Spool Is Sold by the Pound
Every slicer ends its preview with the same two numbers: how long the print will take, and how much filament it will eat. That second figure is almost always in grams, because grams are what a print actually consumes. Spools, though, are catalogued in both systems — a 1 kg roll nearly everywhere, a 1 lb roll on plenty of US shelves — and shipping charges, storage racks and dry-box capacities are frequently quoted in pounds. Converting the gram figure is what lets you say whether a job fits on the roll you already own.
Where the Gram Figure Comes From
The slicer weighs the toolpath
Two spool standards side by side
The unit of cost is the gram
Resin follows the same habit
From Slicer Estimate to Filament Budget
The sequence below assumes a number is already in front of you — the slicer's estimate, a scale reading, or the net weight printed on a spool label.
Enter the mass the slicer reported
Put the gram figure in the left field — 12, 250, 1000, whatever the preview says. The pound value appears as you type. Decimals accept a comma or a dot, and stray spaces are ignored.
Hold it against the roll you own
A 2.2046 lb job needs a full kilogram spool and leaves nothing behind; the same print would swallow almost five pound-rolls in a row. Seeing both numbers together is what prevents a run-out halfway up a tall part.
Copy the bare number into your cost sheet
The copy button hands over the plain figure with no unit and no spaces — exactly what a spreadsheet cell or a quoting form expects. Ctrl + C inside a field does the same thing.
Reverse it for a pound-labelled spool
Press the swap button (↔) to run lb → g when a listing quotes 2 lb or 5 lb and you need the equivalent in slicer grams. By hand, multiply by 453.59237: a 2 lb roll is 907.18 g.
Spool Sizes and Print Masses, Grams Against Pounds
Retail spool capacities plus a few representative print masses, shown as the gram figure you meet in a slicer or on a label and as its pound equivalent.
| Item | Mass (g) | Mass (lb) | Notes |
|---|---|---|---|
| Calibration boat | 12 g | 0.0265 lb | 0.2 mm layers, light infill |
| Small vase-mode print | 45 g | 0.0992 lb | Single wall, no infill |
| Sample / trial spool | 250 g | 0.5512 lb | Common size for a colour test |
| Pound spool | 453.59 g | 1 lb | US retail size, net material |
| Helmet shell segment | 600 g | 1.3228 lb | Large cosplay part at 15% infill |
| Short spool | 750 g | 1.6535 lb | Offered by several speciality brands |
| Standard spool | 1,000 g | 2.2046 lb | The default 1 kg roll |
| Bulk spool | 2,300 g | 5.0706 lb | 2.3 kg roll, needs a wide holder |
| Production spool | 5,000 g | 11.0231 lb | Print-farm and continuous-run size |
Notice how fast the two systems drift apart. A pound roll is not "roughly the same" as a kilo roll — it is 45.4% of one, and a workshop that plans in pounds while its slicer plans in grams will under-order on every job until the two are reconciled.
What Helps When You Are Pricing Prints
Walk a whole print queue in one sitting
Both fields stay live, so you can retype job after job — 84 g, 310 g, 1,240 g — and read off the pound column without clearing anything in between.
Flip when a listing quotes pounds
The swap button turns the page into lb → g, the direction you want when a store sells by the pound and your slicer only understands grams.
Kilograms and ounces on the same dropdowns
Both sides list every weight unit, so a 2.3 kg bulk roll or an ounce-labelled resin bottle passes through the same two fields without leaving the page.
Figures clean enough for a quote
Results carry up to eight decimals — far more resolution than any filament scale offers — and the copy button strips the unit so the number drops straight into a cost formula.
Filament Weight Questions
Does a "1 kg spool" weigh 1 kg when it arrives?
No — that label states net material only. The plastic or cardboard core adds roughly 150 g to 300 g on top, so a full roll commonly reads somewhere near 1,200 g gross, about 2.65 lb, on a kitchen scale. Manufacturers publish empty-core masses and hobbyist databases collect them; write yours on the side of the spool once and you never have to guess again.
How do I work out the cost per gram from a spool price?
Divide the price by the net grams on the label, never by the boxed weight. A $24.99 kilogram roll is $24.99 ÷ 1,000 = $0.02499 per gram, so a part the slicer estimates at 250 g costs about $6.25 in material. When a rival roll is priced by the pound, convert before comparing: 453.59 g at that same rate would be $11.34, which puts the two offers on one scale.
Why is the slicer's gram estimate more useful than the metres of filament it reports?
Length only means something for one diameter and one density. The same 100 m draws a very different amount of material at 1.75 mm than at 2.85 mm, and PLA, PETG and ABS differ again in density, so lengths cannot be compared across materials. Mass is what you paid for, what the label states and what a scale can confirm — which is why costing, ordering and remaining-material checks all run on grams.
How much does infill percentage change the mass of a part?
Less than people expect on small parts and a great deal on large ones. Walls plus top and bottom layers are a fixed cost that dominates anything thin, so pushing a 12 g trinket from 15% to 40% may add only a couple of grams. A chunky block is mostly interior, and the same change can nearly double it. The dependable method is to slice both settings and compare the two gram figures rather than scaling by hand.
Can I tell how much filament is left by weighing the spool?
Yes, and it beats squinting at the roll. Put the spool on a kitchen scale, subtract the empty-core mass, and the remainder is usable material. A roll reading 640 g gross with a 190 g core holds 450 g — just under 0.99 lb — so a 500 g job will not finish on it. Do this before starting anything long and a nervous guess becomes a number.
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