How to Estimate Board Feet in a Standing Tree: A Guide to the Timber Volume Calculator

Board feet is the unit most Michigan sawtimber is bought and sold in, and it is one of the most confusing numbers a landowner runs into. The same tree can hold 74 board feet or 130, depending on which log rule does the measuring. The Standing Timber Volume Calculator lets you see that for yourself, one tree at a time.

The calculator is free. It runs in a web browser on a computer or phone and needs no account. This guide covers how to measure a tree for it, what each setting does, how the tally and export work, and, just as important, what an estimate like this leaves out.

What the calculator does

Give the calculator a tree's species, its diameter at breast height and its merchantable height, and it estimates the volume of the usable stem. You can read that volume under three log rules, Doyle, Scribner and International ¼-inch, or in cubic feet. Add trees to a tally and it keeps a running total you can export to a spreadsheet.

It is an educational tool. It uses general assumptions about taper and bark in place of measuring each log, and it knows nothing about grade, defect or markets. That makes it a good way to learn how measurements and log rules move a number, and a poor way to price timber.

Measure a tree for the calculator

You need two measurements from the tree and one choice about it.

Diameter at breast height

Diameter at breast height, or DBH, is the trunk's diameter 4.5 feet above the ground, measured on the uphill side. A diameter tape wrapped around the trunk reads it directly. With an ordinary tape measure, measure around the trunk and divide by 3.14. Enter it in inches; half inches are fine.

Merchantable height

Merchantable height is the length of stem a sawmill could use: from the stump up to where the trunk forks, turns too crooked or defective, or narrows below a usable top. The calculator takes it two ways. Logs (16 ft) counts 16-foot logs, and half logs are allowed, so 2.5 means two and a half logs. Merch ft takes the length in feet.

Foresters usually judge log height by eye and check it with a clinometer or a known length. If you are new to it, practice on a few trees: note a mark at a known height on the trunk, step back, and count 16-foot sections up the stem before trusting your eye.

Tree type and species

Choose Hardwood or Softwood, then the species. The list covers 25 common Michigan trees: 17 hardwoods, from red and white oak to black walnut, black cherry and the maples, and 8 softwoods, from red and white pine to hemlock and northern white cedar. In this version, the species sets the starting top diameter for cubic volume. The board-foot rules work from diameter and height alone.

Three log rules, three answers

A log rule is a formula or table that predicts how many board feet of lumber a mill will saw from a log. Three are in common use in the United States, and they disagree, most of all on smaller logs.

• Doyle dates from the 1800s. It subtracts a flat four inches from the log's diameter to allow for slabs and edgings, which takes a large bite out of small logs and matters less on big ones.
• Scribner comes from diagrams of boards drawn inside circles the size of log ends. For most logs it falls between the other two. The calculator uses a formula approximation of Scribner, labeled that way on the button, rather than a regional table.
• International ¼-inch is built from a model of sawing with a quarter-inch saw kerf, with an allowance for taper. Of the three, it comes closest to what a mill actually produces.

Here is what the calculator reports for the same trees under each rule:

• 14 inches, 2 logs: Doyle 74, Scribner 112, International ¼-inch 130 board feet.
• 18 inches, 2 logs: Doyle 202, Scribner 247, International ¼-inch 270 board feet.
• 22 inches, 2½ logs: Doyle 466, Scribner 517, International ¼-inch 550 board feet.
• 26 inches, 3 logs: Doyle 875, Scribner 913, International ¼-inch 970 board feet.
• 30 inches, 3 logs: Doyle 1,331, Scribner 1,326, International ¼-inch 1,390 board feet.

At 14 inches, Doyle credits the tree with a little over half of what International ¼-inch does. By 30 inches, the three rules are within about 5 percent of one another. That is why the rule written into a timber sale contract matters most in stands of small and mid-sized sawtimber, which describes most Michigan woodlots, and why two offers quoted under different rules cannot be compared number for number.

Cubic feet and Pro mode

Choose Cubic ft to see the stem's volume in cubic feet instead of board feet. Cubic volume measures all the wood in the usable stem, with no allowance for sawing losses, which makes it a steadier way to compare trees of very different sizes.

Cubic volume needs one more number: the top diameter where the usable stem ends. The calculator fills in a starting assumption for each species, from 6 to 10 inches depending on the tree, and you can change it. The top diameter affects only the cubic-foot figure.

Pro mode, the Basic and Pro switch at the top of the calculator, shows the cubic-foot estimate beside the board-foot result, so you can see both at once.

Build a tally and export it

Add to tally saves the current tree to a list below the calculator. Enter the next tree and add it, and the tally keeps a count and a running total. Remove a tree with the × beside it, or clear the whole list.

The tally stores your measurements rather than the volumes, so switching the log rule recalculates every tree at once. It is the quickest way to see what a rule change does to a whole group of trees.

The tally stays in your browser on that device, so it is still there when you come back. Nothing is uploaded. If your browser blocks storage, the calculator tells you so, and the list lasts only until you close the tab.

Export CSV downloads the tally as a spreadsheet file that opens in Excel, Google Sheets or Numbers. Each row lists the species and its scientific name, the DBH and height, the rule in use, the volume and the time you added the tree. Every row also carries the method version and a plain statement of what the estimate is not meant for.

What an estimate like this leaves out

The calculator estimates the volume in a sound, straight, typical stem. Real trees are rarely that tidy, and volume is only one part of what timber is worth.

• Grade. A clear white oak butt log and a knotty one of the same size can differ enormously in value.
• Defect. Rot, seams, sweep and old fence wire all reduce what a mill can use. The calculator assumes none.
• Taper and bark. Both vary by species and site. The calculator uses one general assumption for all trees.
• Markets and access. Price depends on species, grade, mill demand, haul distance, the season and how the sale is set up.
• Sampling. A handful of measured trees says little about a whole stand unless they were chosen by a proper sampling design.

So use the numbers to understand what you hear from a buyer or a forester, and to see how much the log rule matters. For a sale, an appraisal, a tax question or a contract, you need a timber cruise: a systematic measurement of the trees by someone who grades them and knows the local markets.

Using it well

1. Measure DBH carefully. On an 18-inch, two-log tree, one inch of diameter moves the Doyle estimate by about 20 percent.
2. Be honest about merchantable height. Stop the count where a mill would stop: at a fork, heavy limbs, a bad crook or rot.
3. When you compare numbers, use the rule your buyer or contract uses, and write down which rule you mean.
4. Keep a tally as you walk and export it, so you have a record to bring to a conversation with a forester.