Dr. John A. Kershaw, Jr. CF, RPF, Forest Mensurationist

“The really great forester combines technical knowledge with idealism; even though he may be mistaken in detail, he must be enough of a thinker to fathom the national needs of the future.” – Theodore S. Woolsey, Jr. (Riding the Chuck Line)

PR Calculator

PRCalc is a stand-alone Windows based program that calculates percent volume of timber products for a given tree list or stand table and product specifications. The program utilizes the merchantable volume ratios approach outlined in Honer et al. (1983). It can be used to assess stand value and to examine effects of varying species dimensional specifications for timber products. PRCalc develops merchantable ratios for both metric and Imperial units.


The Install files for PRCalc are found HERE

Unzip the files into a common directory (TEMP) and run Setup

About PRCalc

PRCalc uses Honer et al.’s (1983) merchantable volume ratios to estimate product ratios (percent total volume in defined product classes: sawlogs, studwood, pulp, etc.). Products are defined by /species, minimum top diameter and log length. Products are sorted by minimum top diameter (largest to smallest) and percent volume allocated to largest to smallest product classes.

See: Kershaw, Richards and Larusic. In Press. A Product Ratio Calculator for Northeastern Tee Species. Northern Journal of Applied Forestry for complete details.

A pdf of the submitted article is found HERE

PRCalc uses a spreadsheet-like like interface:

PRCalc requires two inputs:

Product Specifications:

Species – common name or two letter species code (see below for list of allowable names)

Top Diameter (inside bark) – in centimeters or inches (depending on units selected)

Log Length – in meters or feet (depending on units selected). Enter 0 for whole tree or variable length

Stock Table (or Tree List):

Species – must use same convention as used in Product Specifications (above)

DBH – diameter at breast height in centimeters or inches

Total Height – feet or meters

Inputs may also be cut and pasted from a spreadsheet program as well.

Once all inputs are entered, the [Calculate Product Ratios] button is pressed and the output window appears:

Output Consists of:

Species – Corresponds to species in Stock Table (Tree List)

Product – Product name corresponding to Product List for Species

Ratio (%) – Product Ratio (% Total Volume)

Num. Logs – Number of logs in given species-product

Each line in output corresponds to a tree in the Stock Table and Product in the Product Specifications. So for the example shown above, the first two lines in the output table corresponds to the first tree and the two hardwood products: sawlogs and pulpwood. Thus, the 20 cm, 16 m tall hardwood has no sawlogs and 5 pulp logs making up 97% of the total volume:


Species may be specified either by common name or two letter code. The following species are recognized by PRCalc:

white pine WP

red pine RP

jack pine JP

lodgepole pine LP

black spruce BS

red spruce RS

white spruce WS

balsam fir BF

other conifer OC

poplar PO

white birch WB

yellow birch YB

other hardwood OH

average species AS

Unrecognized species default to average species.

PRCalc is provided free of charge and there is no real or implied guarantee. Product ratios are derived from the largest product to the smallest product and tree utilization is not optimized. Users are strongly recommended to test ratios locally since the merchantable ratios were originally derived from a vast regional database.

If you discover any odd behavior, errors or bugs, please let me know and I’ll try to fix them.