How to estimate a metal cutting job
Three things matter when planning a cutting job: how long it takes to cut, how much the parts weigh, and how efficiently they fit onto a sheet. This calculator handles all three for plasma, laser or waterjet — just enter your part, material and sheet size.
Cut time
Cutting time has two parts. Travel time is the cutting path length divided by the cutting speed. Pierce time is the few seconds the machine spends punching through the material at the start of each cut or hole. Parts with lots of holes can spend surprising amounts of time piercing, so it's counted separately.
Part weight
Weight is the part area times the thickness (the volume), times the material density. Mild steel is about 7.85 g/cm³, aluminium about 2.70 and stainless about 8.00. Useful for handling, shipping and material planning.
Sheet nesting
Parts are laid in a grid allowing for the gap between them and an edge margin, testing both orientations and keeping whichever fits more. That gives the parts per sheet and how many sheets the order needs. The material-used figure shows how much of each sheet becomes parts rather than offcut.
Cutting speed by process
Speed varies a lot with process, power and thickness, and doubling the thickness often roughly halves the speed. As a guide for 12 mm mild steel, plasma runs around 1,500 mm/min, laser around 1,200 mm/min and waterjet around 450 mm/min. For accuracy, use the real figure from your own machine.
Frequently asked questions
How do I calculate metal cutting time?
Cut length ÷ cutting speed gives travel time; add pierce time (pierces × seconds per pierce) for the total per part.
How do I calculate the weight of a cut metal part?
Multiply part area by thickness for the volume, then by the density — steel ≈7.85, aluminium ≈2.70, stainless ≈8.00 g/cm³.
How do I work out how many parts fit on a sheet?
Lay them in a grid allowing for the gap and edge margin, trying both orientations. Columns × rows that fit gives parts per sheet.
What cutting speed should I use?
It depends on process, power and thickness — doubling thickness often roughly halves speed. For 12mm mild steel: plasma ≈1500, laser ≈1200, waterjet ≈450 mm/min.