Is 1.75 mm or 2.85 mm the right diameter?

Most modern printers use 1.75 mm. Some older Prusa and Ultimaker models use 2.85 mm.

Filament Weight Calculator — Length to Grams

Q: What density should I use?

PLA 1.24, PETG 1.27, ABS 1.04, TPU 1.21, Nylon 1.14 g/cm³ — check your spool's spec sheet.

Your inputs

Your result

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Enter your values to see the filament weight

Knowing how much a given length of filament weighs is useful in several practical situations: estimating how much filament a print will use before slicing, checking whether the remainder on a spool is enough for a job, or cross-referencing your slicer's grams output against a physical length measurement. This calculator uses the exact cylindrical volume formula to give you a precise result for any material diameter and density.

The formula, explained step by step

Filament is a long, thin cylinder. To find its weight, you calculate the volume of that cylinder and multiply by the material's density.

Step 1 — Calculate the cross-sectional area:
Area = π × (diameter ÷ 2)²
For 1.75 mm filament: radius = 0.875 mm = 0.0875 cm
Area = π × 0.0875² = π × 0.007656 ≈ 0.02405 cm²

Step 2 — Calculate the cylinder volume:
Volume (cm³) = Area × length (in cm)
10 meters = 1000 cm
Volume = 0.02405 × 1000 = 24.05 cm³

Step 3 — Multiply by material density:
Weight (g) = Volume (cm³) × density (g/cm³)
For PLA at 1.24 g/cm³: 24.05 × 1.24 = 29.82 g

Notice that all calculations happen in centimeters: the diameter in mm is divided by 10 to get cm, and the length in meters is multiplied by 100 to get cm. Keeping units consistent is the most common source of errors when doing this calculation by hand.

How to use this calculator

Measure or know the filament length. If you're checking a remaining spool, you can estimate length using our Filament Length Calculator (weigh the spool, subtract the empty spool weight, then convert grams to meters). For a specific design question (e.g., "how heavy is 5 meters of support structure?"), enter the length directly.
Set the diameter. Use 1.75 mm for virtually all modern consumer FDM printers. Use 2.85 mm for older Ultimaker 2/3 printers, some Prusa original designs, and niche industrial machines. Measure your filament with calipers if in doubt — budget filaments sometimes have diameter tolerance issues of ±0.1 mm.
Set the material density. Use the table below. If you're using a specific brand with a known density spec, use that value. The difference between 1.24 and 1.27 g/cm³ (PLA vs. PETG) amounts to about 2.4% change in weight per meter — noticeable when working precisely.
Read the result. The calculator shows both volume in cm³ and weight in grams. The volume is useful if you're cross-referencing with slicer software that sometimes reports material volume.

Complete density reference table

These are standard reference densities. Individual brands may vary by ±2–3%:

PLA (standard) — 1.24 g/cm³
PLA+ / PLA Pro — 1.17–1.24 g/cm³ (varies by formulation; additives change density)
PETG — 1.27 g/cm³
ABS — 1.04 g/cm³
ASA — 1.07 g/cm³ (similar to ABS but UV-resistant)
TPU (flexible, 95A) — 1.21 g/cm³
TPE (softer flexible) — 1.20 g/cm³
Nylon (PA6 / PA12) — 1.14 g/cm³
Nylon + CF (carbon fiber reinforced) — 1.10–1.17 g/cm³
PC (Polycarbonate) — 1.20 g/cm³
PEI / PEEK — 1.26–1.30 g/cm³
HIPS — 1.04 g/cm³
PVA (water-soluble support) — 1.19–1.23 g/cm³
Wood fill PLA — 1.20–1.28 g/cm³ (depends on wood fiber %)
Glow-in-dark PLA — 1.24–1.30 g/cm³ (phosphorescent additives add weight)
Metal fill (copper, bronze, iron) — 1.5–3.0 g/cm³ (significantly heavier)

Real-world use cases

Case 1: Checking spool remaining before a long print

You have what looks like about 8 meters of PLA left on a spool. Your Bambu Studio reports your next print uses 23 g. 8 meters of 1.75 mm PLA weighs: π × 0.0875² × 800 cm × 1.24 ≈ 23.85 g. You'll just barely have enough — but should consider whether the estimate is accurate. In this case, weigh the spool instead for a definitive answer.

Case 2: Estimating support structure weight for a quote

You estimate your model will need roughly 3 meters of support structure in PETG. Weight: π × 0.0875² × 300 cm × 1.27 ≈ 7.30 g. At $28/kg, that's $0.20 in support material waste — worth knowing when quoting complex parts.

Case 3: Comparing PLA vs. metal-fill for a prop

A client wants a prop to "feel heavy." 20 meters of standard PLA weighs 59.6 g. The same 20 meters in iron-fill PLA (density ≈ 2.4 g/cm³) would weigh 115.5 g — nearly double. Combined with post-print polishing, the result has both the visual and tactile qualities of metal. The weight calculation informs the material choice decision.

Case 4: Calibrating your extruder

Mark exactly 100 mm of filament before it enters the extruder. Command the extruder to feed 100 mm. Measure how much actually moved. If you fed 100 mm of 1.75 mm PLA and it weighs 0.298 g, your extrusion is consistent with the formula. Discrepancy indicates calibration drift — useful when diagnosing over/under extrusion issues.

Why diameter accuracy matters more than you think

Weight scales with the square of the radius. A 0.1 mm diameter difference changes the weight by:

1.75 mm vs. 1.85 mm: (1.85/1.75)² = 1.118 — an 11.8% weight difference per meter. Budget filaments with poor diameter consistency (±0.1 mm is common) can cause print quality issues precisely because the extruder is calibrated for a consistent diameter. A $5 set of digital calipers measured at multiple points along a filament strand tells you whether your filament is consistent enough for precision work.

Common mistakes

Mixing up diameter and radius. The formula uses the radius (diameter ÷ 2) squared, not the diameter squared. Using the diameter directly would overestimate the weight by 4×. The calculator handles this automatically.

Using the wrong units. The formula requires consistent units — all in centimeters. 1.75 mm = 0.175 cm diameter, 0.0875 cm radius. 10 meters = 1000 cm. Mixing units is the most common manual calculation error.

Assuming all "PLA" has the same density. PLA+ formulations can have densities from 1.17 to 1.24 g/cm³ depending on additives. For precise work, check your specific brand's TDS (technical data sheet) — usually available on the manufacturer's website.

Recommended: A $10 digital caliper lets you measure filament diameter at multiple points to check consistency — essential if you're using budget filament or experiencing extrusion issues.

Frequently asked questions

What density should I use for PLA?

Standard PLA is 1.24 g/cm³. PLA+ formulations vary from 1.17 to 1.24 g/cm³ depending on the specific additives. Silk PLA is typically around 1.24 g/cm³. If your spool has a technical data sheet (most quality brands publish one), use the density listed there. For general estimates, 1.24 g/cm³ is accurate within 2–3% for most PLA variants.

Is 1.75 mm or 2.85 mm the standard?

1.75 mm is the de facto standard for modern consumer FDM printers — Bambu Lab, Prusa MK4, Creality Ender series, Voron designs, and the vast majority of machines. 2.85 mm (sometimes called 3 mm) is used in older Ultimaker 2/3 printers, certain Prusa industrial models, and some niche machines. If your printer accepts 2.85 mm, your spool will be clearly labeled. When in doubt, measure the filament with calipers.

Why does my result differ from the slicer's filament estimate?

This calculator gives the weight of a straight cylinder of filament of a given length. A slicer calculates the actual extrusion path for a specific model — including infill patterns, perimeters, support structures, skirt lines, and travel moves with no extrusion. The slicer's output accounts for all the geometry of the print; this calculator gives you the basic material mass for a known length. The two are related but not identical.

How do I measure the length of filament on a partial spool?

The practical way is to weigh the spool and use our Filament Length Calculator: weigh the spool, subtract the empty spool weight (printed on the label or available from the manufacturer), then convert the remaining grams to meters. Direct measurement of filament length by unwinding is time-consuming and impractical for large amounts.

What is the weight of a full 1 kg spool of PLA in meters?

1000 g ÷ (π × 0.0875² cm² × 1.24 g/cm³ per cm) ≈ 1000 ÷ 0.02981 ≈ 33,546 cm ≈ 335 meters. This is why filament is often sold with length specs of about 330–340 m per kg. For PETG (1.27 g/cm³), it's slightly less: ~327 m/kg. For ABS (1.04 g/cm³), it's more: ~399 m/kg.

Does filament diameter affect print quality?

Yes, significantly. Your slicer and extruder are calibrated for a specific diameter. If the filament varies significantly from the stated diameter (more than ±0.05 mm), the extruder can't maintain consistent flow, causing under-extrusion or over-extrusion zones. Quality filament brands maintain ±0.02 mm tolerance; budget brands can be ±0.1 mm or worse. This is why measuring with calipers at multiple points reveals filament quality issues before they cause a failed print.

Does moisture affect filament weight?

Yes, hygroscopic filaments (Nylon, PETG, PVA, TPU) absorb atmospheric moisture and become heavier over time. A wet Nylon spool can weigh 1–3% more than when new. More importantly, wet filament prints poorly — causing bubbling, stringing, rough surfaces and weak layer adhesion. Dry your filament with a food dehydrator, dedicated filament dryer, or oven at 50–70°C before use if it's been exposed to air for more than a few days.

How accurate is this calculator compared to physically weighing filament?

The formula is mathematically exact, so the accuracy depends on your inputs. If you know the length precisely and use the correct density, the result matches a physical measurement within 1–2%. The main source of error is density variation between brands and batches — even the same "PLA" from different manufacturers can vary by 2–4% in density. For critical weight budgets (e.g., aerospace or weight-sensitive drones), weigh your actual prints rather than relying on calculated estimates.

Why do metal-fill filaments weigh so much more?

Metal-fill filaments contain real metal powder (copper, bronze, iron, stainless steel) suspended in a PLA carrier. Metal powders have densities of 7–9 g/cm³ vs. PLA's 1.24 g/cm³. Even at 50% fill by volume, the resulting composite density can reach 2.5–4 g/cm³ — 2–3× heavier than standard PLA per meter. This is intentional: the goal is prints that feel and, after polishing, look like solid metal castings.

Filament Weight Calculator