Measuring Trees and Timber Volume

What do foresters actually measure on a tree?

Most timber work starts with two basic measurements: the width of the trunk at about chest height, and how tall the usable part of the stem is. Width is taken with a special tape or a caliper. Height can be judged with a simple hand-held gauge or a clinometer, which measures angles so you can work out height from a known distance.

Foresters often describe the usable height in logs rather than total feet, because a sawmill pays for the straight, clear section of the trunk, not the crooked top. Two trees of the same width can be worth very different amounts if one has a long clean stem and the other forks low.

How is timber volume calculated?

Volume is estimated by combining trunk width and merchantable height using a table or formula called a volume rule. Different regions use different rules, and they can give noticeably different totals for the very same tree. That is why a buyer and a seller need to agree on which one is being used before any number is quoted.

Board feet is the unit most people hear for sawtimber, while pulpwood and firewood are often sold by weight or by the cord. Ask any buyer to state the unit and the rule in writing. Your state forestry agency or extension office can explain which rules are common where you live.

What is a timber cruise?

A timber cruise is a sample-based inventory of a stand. Instead of measuring every tree, a forester walks a pattern across the woods, measures trees at set sample points, and scales the results up to the whole area. The sample also records species, quality and health.

A cruise gives you a defensible estimate of volume by species and grade, which is the information you need to compare bids. Doing it yourself is possible for personal curiosity, but a sale decision made on a rough guess is where landowners most often lose money.

• Species mix matters because prices differ widely between species
• Grade matters because clear logs bring far more than knotty ones
• Defects such as rot, sweep and old wire or nails reduce usable volume

Can I measure my own trees at home?

Yes, and it is a good way to learn your woods. A diameter tape, a pocket calculator and a notebook go a long way. Pick a small plot, mark it, measure every tree above a chosen width, and note the species and any obvious problems.

Treat your numbers as a starting point for a conversation, not as a price. Home measurements tend to overestimate because they miss hidden defects and the way a sawmill trims a log. Share your notes with a forester and let them tell you how close you came.

Many landowners find that their first plot teaches them more about their woods than years of walking through them. You begin to notice which trees are growing fast, which are struggling and where the crowding is worst.

Why do measurements matter beyond a sale?

The same data guides thinning, planting and wildlife decisions. If the woods are crowded, measurements show it. If one species dominates, they show that too. Keeping a simple record every few years lets you see growth and spot trouble early.

Records also help with estate planning conversations and with conservation programs, where an official plan often needs an inventory. Ask your local NRCS office or state forestry agency what documentation they want before you spend time collecting it.

Who can help me learn to measure?

Many extension offices and state forestry agencies run woodland owner workshops where you can practice with the real tools on real trees. These are usually low pressure and a good place to meet neighbors with similar woods.

Be cautious of anyone who offers a free, quick estimate and then pushes you to sign. A measurement with a sales pitch attached is not neutral information.

What common mistakes should I avoid?

The biggest error is mixing up units. A figure in board feet, a figure in cords and a figure in tons cannot be compared without conversion, and a bid can look generous simply because it uses a different unit. Another mistake is measuring only the best-looking trees and assuming the rest match them.

Also avoid measuring in a hurry in poor light or on steep ground. Write every number down on the spot, record the species beside it, and note the date. A tidy record from one afternoon is worth more than a memory of several.

• Check units on every quote
• Measure a representative sample, not just the showpieces
• Record species and defects beside each number

Last reviewed: November 12, 2026. Written by the Rural Farm Life Editorial Team. See our editorial policy.