How long does a 1 kg filament spool last
Metres per kilo for every material, in 1.75 and 2.85 mm, and how many typical parts come out of a full spool.
A 1 kg spool of 1.75 mm PLA holds about 335 metres of filament. In 2.85 mm the same kilo comes to about 126 metres, because the strand is much thicker. And in ABS, which weighs less per cubic centimetre, the kilo reaches about 400 metres. The full table:
| Material | Density (g/cm³) | 1 kg in 1.75 mm | 1 kg in 2.85 mm |
|---|---|---|---|
| PLA | 1.24 | 335 m | 126 m |
| PLA+ | 1.24 | 335 m | 126 m |
| PETG | 1.27 | 327 m | 123 m |
| ABS | 1.04 | 400 m | 151 m |
| ASA | 1.07 | 389 m | 146 m |
| TPU (flexible) | 1.21 | 344 m | 130 m |
| Nylon (PA) | 1.14 | 365 m | 138 m |
| PC (polycarbonate) | 1.20 | 346 m | 131 m |
| Wood / PLA | 1.15 | 362 m | 136 m |
| Carbon fibre / PETG | 1.30 | 320 m | 121 m |
Where those metres come from
No mystery: filament is a cylinder. You divide the weight by the density to find how many cubic centimetres of plastic there are, and divide that volume by the cross-section of the strand. A 1.75 mm filament has 0.0241 cm² of section; a 2.85 mm one has 0.0638 cm², that is 2.65 times more. You can run the conversion with your own numbers in the filament grams to metres converter.
How many parts come out of a spool
| Part | Weight | Units per spool | Filament per unit |
|---|---|---|---|
| Custom keyring | 5 g | 200 | 1.7 m |
| Tabletop miniature (32 mm) | 8 g | 125 | 2.7 m |
| Phone stand | 25 g | 40 | 8.4 m |
| Articulated figure (dragon) | 55 g | 18 | 18.4 m |
| Small planter (8 cm) | 60 g | 16 | 20.1 m |
| Drawer organiser | 90 g | 11 | 30.2 m |
| Box with lid (10 cm) | 110 g | 9 | 36.9 m |
| Large planter (15 cm) | 180 g | 5 | 60.4 m |
| Cosplay mask | 320 g | 3 | 107.3 m |
| Full cosplay helmet | 900 g | 1 | 301.8 m |
Careful with these figures: they are the theoretical maximum. In practice you have to knock off the filament stranded on the core — the last 3 to 5 metres can't be printed safely — the purges when you change colour, and the failed prints. Counting on 90% usable is realistic.
How long it lasts in time, not metres
Another way to measure it: a 1 kg spool covers about 80 hours of printing at a normal rate of roughly 12 grams an hour. If you print 3 hours a day, that is about a month per spool; flat out, a little over a week. Those 80 hours cost power and machine too: about $1.44 of electricity at 120 W and $0.15/kWh, and around $6 of depreciation on a $300 printer.
How to know what's left on an open spool
- Weigh the whole spool on a kitchen scale.
- Subtract the weight of the empty core: between 200 and 250 g on plastic ones, less on cardboard. Plenty of brands print it on the spool itself.
- What's left is the grams of filament; convert them to metres with the converter.
And before you start a long print, check you'll make it: if you have 40 metres of 1.75 mm PLA left, that is about 120 grams, and a part asking for 130 g will stop halfway through the night.
What each part off that spool costs
Metres are only half the story; the other half is money. The 3D printing cost calculator splits the spool price across the grams in each part and adds power, machine and failures, and how much does 3D printing cost has twenty parts already worked out.
Want the exact number for your own case? 3D printing cost calculator does the full sum with your filament, your electricity tariff and your printer, and leaves the quote ready to copy.
Frequently asked questions
How many metres are on a 1 kg spool of PLA?
About 335 metres in 1.75 mm and about 126 metres in 2.85 mm.
The figure comes from dividing the volume of the kilo of plastic by the cross-section of the strand, and can vary 1-3% with diameter tolerance.
How long does a spool of filament last?
Roughly 80 hours of printing, at an average rate of about 12 grams an hour.
Printing 3 hours a day, that is around a month per spool.
How many keyrings come out of 1 kg of filament?
About 200 keyrings of 5 grams, if none of them fail.
Counting the filament you can't use at the end of the core and the odd failure, about 180 is realistic.
Why does my spool weigh more than 1 kg?
Because the kilo refers to the filament, not the whole thing. The plastic core adds between 200 and 250 grams.
A new «1 kg» spool on the scale usually reads between 1.2 and 1.3 kg.
Can the filament at the end of the spool be used?
The last few metres are tightly curved and pull on the extruder, so they tend to cause trouble on long parts.
They work well for small parts and calibration tests, which is the best way not to throw them away.
Does filament expire?
It doesn't expire, but it absorbs moisture from the air, and that does ruin prints: bubbles, stringing and a rough surface.
PLA survives months in a sealed bag with desiccant; nylon and TPU go off in days if left in the open.
More tools and guides
- 3D printing cost calculatorWork out the real cost and selling price of a 3D printed part: material, power, machine and markup. Free, no sign-up.
- How much electricity does a 3D printer useWork out your 3D printer's electricity use and what it costs per month on your own tariff. Free and instant.
- Filament grams to metres converterConvert grams of filament to metres by material and diameter (1.75 / 2.85 mm). Instant calculation, no sign-up.
- How much to charge for a 3D printed partPrice your 3D printed parts properly: real cost + labour + markup. Free, no sign-up, with a quote ready to send.
- How much does 3D printing cost: 20 parts with real numbersThe real cost of 20 typical 3D printed parts: keyring, planter, phone stand, gear and more.
- Density and price of 3D printing filamentsDensity (g/cm³) and price per kilo for the most used 3D printing filaments, with metres per kilo.