Chipper productivity calculator: how long to chip the brush

It estimates how many hours a crew spends on site clearing a brush pile through a hand-fed chipper, how many cubic yards of chips that leaves, and what those hours cost on the site's crew-hour model. The model treats the job as two rates. One is how fast the crew can carry brush to the infeed. The other is how fast the chipper takes it. The slower of the two sets the pace.

1. Pace the pile and enter length, width and height, or switch to loose cubic yards if you know them.
2. Pick the chipper class and enter the thickest limb in the pile, so the capacity check can flag it.
3. Enter the drag distance, from the middle of the pile to the infeed table, and the people on brush.
4. Read the hours on site, then look at the assumptions. If your crew is faster or slower, change that one number.
5. Copy the line into your quote, or print the sheet for the job folder.

Here is how capacity, horsepower and feed-roller speed line up across one maker's range. The feed speed is how fast the rollers pull a limb in. It is not a volume. Brush is mostly air, and a crew can never keep the rollers full, so no maker publishes cubic yards an hour. That is why the intake figure in the calculator is a stated assumption, not a spec.

Every armload is a walk out, a walk back and a few seconds at the infeed. Double the drag and you nearly double the walking. The table runs the calculator's default job at six drag distances. Up to about 50 feet, a three-person crew keeps a 12-inch chipper busy. Past that the crew is the limit, and a bigger chipper saves nothing. On the default job a 15-inch machine cuts the time from 2.0 hours to 1.9.

The fixes that work are the ones that shorten the walk: back the chipper closer, drop the brush nearer the road, or add a person on the far end. At a 150-foot drag, going from three people to four on brush cuts the default job from 3.2 hours to 2.5.

Labour is the site's standard rate: the BLS hourly mean of $26.91 for tree trimmers and pruners, times a 1.55 load for payroll tax, workers' compensation and non-billable time (our assumption), gives $41.71 per crew-member hour. The chip truck and chipper are carried at $45 to $95 per crew hour, and a bid is direct cost times 1.6 to 2.1. The same model runs in the removal calculator and the estimate template, so a brush line here drops straight into a quote.

A pile 20 feet long, 10 wide and 6 high is 1,200 cubic feet, or 44.4 loose cubic yards (27 cubic feet to the yard). With a 12-inch chipper, a 50-foot drag and three people, each trip takes 1.42 minutes and the crew could bring 31.8 yards an hour. The chipper's assumed 30 is the limit, so chipping takes 1.48 hours. Add half an hour to set up and rake out and the job is 2.0 hours on site, 5.9 crew-member hours. Direct cost is $337 to $436, a bid of $539 to $916, and you are left with about 11 yards of chips at 4 to 1.

Eleven yards is more than most driveways want. The mulch calculator shows how much ground that covers at a useful depth. If you are pricing whether to own a machine at all, chipper rental vs hiring a crew runs the numbers, and starting a tree service covers the chipper as a first big purchase.

For line-clearance crews, OSHA's 29 CFR 1910.269(r)(2) requires a locking device in the chipper's ignition. Access panels for the blades and drive train must be in place while it runs. A chipper with no mechanical infeed needs a hopper long enough that nobody can reach the knives. A trailer chipper unhooked from the truck must be chocked, and everyone near the feed table wears the required PPE.