How to work out 3D printing costs in the UK without a calculator

Most people land on a cost calculator because they have a 3MF or STL in front of them and want to know what it should cost to print. The honest answer is that you only need four numbers, and a spreadsheet handles it faster than most of the online tools.

This is how we cost prints in the workshop, what the popular UK calculators get wrong, and when it makes more sense to mail the file to someone who already owns the printer.

What actually goes into the cost of a 3D print

There are four real costs. Everything else is a rounding error or a markup.

• Filament used. Grams of plastic, multiplied by the price per kilo.
• Electricity. Hours of printing, multiplied by the printer's average draw, multiplied by your unit rate.
• Printer wear. A small per-hour figure that covers nozzles, belts, build plates and the printer itself.
• Failure rate. A percentage on top of everything else, because some prints fail and the plastic still got used.

If a calculator asks you for more than this, it is either padding for a paid tier or trying to look clever. If it asks you for less, it is hiding something.

How to estimate filament use

Slice the file. That is the only accurate way. OrcaSlicer, Bambu Studio, PrusaSlicer and Cura all tell you grams used after slicing — usually within a gram of reality on a well-tuned machine.

If you do not have a slicer installed, you can guess from the model's volume in cm³. PLA is roughly 1.24 g per cm³, PETG about 1.27, ABS about 1.04, TPU about 1.21. Multiply the solid volume by infill percentage, add about 5 grams for walls and supports on anything bigger than a coaster, and you have a rough number. Rough being the operative word — a 200g part can come out 30g lighter or heavier depending on infill pattern and wall count.

UK filament prices in 2026 sit at roughly £15-25 per kilo for decent PLA and PETG, £25-40 for ABS and ASA, £35-60 for TPU, and anywhere up to £80 for engineering filaments like PA-CF or PC.

How to estimate electricity

A modern bed slinger like a Bambu A1 or Prusa MK4 averages around 100-150 watts during a print. A CoreXY with an enclosed chamber like a K2 Plus or X1C runs higher — 150-250 watts on average, more during heat-up. Resin printers are lower still, usually under 100 watts.

Multiply average watts by hours, divide by 1000, and multiply by your unit rate. At a typical UK rate of around 25-30p per kWh (check your own bill — it varies wildly), a 10-hour PLA print on a sensible FDM machine costs you somewhere in the region of 30-50p in electricity. Not nothing, but not the dominant cost either.

The dominant cost is almost always the filament.

What most cost calculators get wrong

They ignore failures. A calculator that tells you a print costs £4.20 is telling you what one successful print costs in plastic and power. If you fail one in ten prints — which is generous for an untuned machine on a fiddly model — your real cost per finished part is closer to £4.70. Production shops factor in 5-15% failure depending on the material.

They ignore wear. Nozzles wear out, especially on abrasive filaments. Build plates lose their grip. Belts stretch. PTFE tubes degrade. Over the life of a hobbyist printer this works out to something like 5-15p per hour of printing for a well-maintained FDM machine. Commercial operations charge more, because they also factor in the depreciation of the printer itself.

They give you a flat per-gram rate. Real filament use is not linear with model size. A small detailed model can be 80% walls and supports. A big chunky model can be 90% infill. A flat "PLA costs 4p per gram printed" rule produces nonsense at both ends.

They forget post-processing. Supports take time to remove. Multi-colour prints take time to clean. Painted models need primer, paint and drying time. If you are quoting someone else for a print, that time is real money.

A worked example

Let us say you slice a 120g PETG model that takes 9 hours to print on a CoreXY.

Filament: 120g at £22/kg = £2.64. Electricity: 9 hours at 180W average and 28p/kWh = about 45p. Wear: 9 hours at 10p = 90p. Failure margin at 10%: add roughly 40p.

That lands at around £4.40 in true cost. If you are printing it for yourself, that is your number. If you are printing it for someone else and your time is worth anything at all, the price needs to be higher — you have to load and unload the machine, clear failures, package the part and answer the customer's emails.

Is it worth using a paid calculator?

For a one-off print, no. The slicer tells you grams and hours; a £0 spreadsheet does the rest.

For a small business running 50+ prints a month across multiple materials, yes — but the value is in the tracking, not the maths. Tools like 3DPrinterOS, Octoprint plugins or even a Google Sheet with formulas pay for themselves by stopping you from accidentally underquoting a job.

What to ignore: anything that quotes you a price before you upload a sliced file. Any tool that costs a print from "size in mm" is guessing.

When the maths is not the hard part

The maths is easy. The hard part is owning a printer that is set up correctly for the material you want to use.

A quoted £4.40 print is only £4.40 if your bed is flat, your flow is calibrated, your retractions are dialled in and you have the right filament in stock. Otherwise it is three failed prints, a clogged nozzle and a Friday evening that did not go the way you planned.

That is the situation we hear about most often — someone has a model they really want printed, the calculator says it should cost a fiver, and the printer they bought to do it is somewhere between unreliable and untouched in a cupboard.

When to mail it in

If you have a 3MF or STL and you would rather just have the finished part in your hands, send it to us. Drop the file at /contact.html (or use the print upload form on the home page) and we will slice it, quote it, print it and post it back. Materials, colours and slot counts are priced on our printing page, and our quotes include the failure margin, the wear, the electricity and the labour, so the number you see is the number you pay. UK mail-in only — share the address once we have agreed the job.