What you practice
Pick your contest's rules and a level. DBH and height draws one instrument at a time: a Biltmore stick across the trunk, the Merritt log face beside a tree seen from 66 ft, a d-tape at its zero line, or a clinometer for Idaho's total height. Tree volume turns measurements into volumes from the contest's table. Plot tally is the whole practicum: a plot of 8 to 10 drawn trees, a tally to fill, and the volume per acre, scored the contest's way. Prism point has borderline trees, basal area and trees per acre. Teachers can print a class set with a different plot for each student.
Example: the 2023 National FFA key
The National FFA published key for its 2023 timber cruise lists ten trees: 14 in with 1 log (52 bd ft), 13 in with 1 log (42), 16 in with 2 logs (125), 15 in with 2 (104), 16 in with 1 1/2 (101), 16 in with 1 (77), 15 in with 2 (104), 28 in with 2 1/2 (700), 25 in with 2 (443) and 16 in with 1 1/2 (101). Every value comes from the Doyle form class 80 table, and the total is 1,849 bd ft. With the plot counted as 1 acre, that is the volume per acre. Try a National plot
Questions
How do I read a Biltmore stick for DBH?
Hold the stick level against the tree at 4 1/2 ft, 25 in from your eye. Line up zero with the left edge of the trunk and, without moving your head, read the mark nearest the right edge. That mark is the DBH to the nearest inch.
How do I count logs with a Merritt hypsometer?
Stand 66 ft from the tree, hold the log face upright 25 in from your eye with zero on the stump, and read where the merchantable top falls. Contests round down to the half log. To pace 66 ft, divide 66 by your pace length.
Where does merchantable height stop?
National FFA rules stop at a 10 in top inside the bark, at a major fork, or where a limb is half the stem diameter, measured from a 6 in stump. Alabama uses an 8 in top. Every sheet here prints the rules of the contest you pick.
How do I get board feet per acre from a plot?
Look up each tree in the volume table, add them for the plot total, then multiply by the plot's expansion factor: 5 for a 1/5 acre plot, 10 for 1/10 acre. National FFA tells you to treat the plot as 1 acre, so the total is the answer.
How is the timber cruise scored?
National FFA gives 30 points for DBH, 30 for height and 40 for volume, with 5 points off for each full 5% the volume is off: 4.9% off loses nothing, 5.0% loses 5. Georgia takes 1 point per full 1%. After you check a plot here, you see the score your tally would get.
What is a limiting distance with a prism?
It is how far away a tree of a given DBH can stand and still count. Multiply the DBH by the plot radius factor: 2.75 ft per inch for a BAF 10 prism, 3.89 for BAF 5, 1.94 for BAF 20. A borderline tree closer than that is in.
How do I get trees per acre from a prism point?
Each tree that counts stands for BAF divided by its basal area, 0.005454 × DBH², trees per acre. A 10 in tree on a BAF 10 point is 10 ÷ 0.5454 = 18.3 trees per acre. Add the tree factors of every in tree.
Which volume table does my contest use?
National FFA prints a Doyle form class 80 table in its 2026 handbook, and Georgia uses the same one. Idaho uses a Scribner table by total height. Alabama weighs pine plots in tons per acre (its Table I) and uses a Doyle form class 78 table for hardwood, which is what this site practices.
Sources, read October 27, 2026: National FFA Forestry CDE handbook (revised January 2026), its timber cruising instructions and the 2023 timber cruising key; Georgia FFA Sr. Forestry timber cruising score sheet (PDF); Alabama FFA Forestry CDE 2025 (PDF); Idaho Forestry Contest manual, revised 2025 (PDF), chapter 2 Timber Cruising; Clemson LGP 1193, How to Conduct a Timber Cruise: point sampling, limiting distance, tree factors. Plot radius factors here are worked out from the BAF (8.696 ÷ √BAF), not copied from a table.