In forestry, a tree crown measurement is one of the tree measurements taken at the crown of a tree, which consists of the mass of foliage and branches growing outward from the trunk of the tree. The average crown spread is the average horizontal width of the crown, taken from dripline to dripline as one moves around the crown. The dripline is the outer boundary to the area located directly under the outer circumference of the tree branches. When the tree canopy gets wet, any excess water is shed to the ground along this dripline. Some listings will also list the maximum crown spread which represents the greatest width from dripline to dripline across the crown. Other crown measurements that are commonly taken include limb length, crown volume, and foliage density. Canopy mapping surveys the position and size of all of the limbs down to a certain size in the crown of the tree and is commonly used when measuring the overall wood volume of a tree.

Average crown spread is one of the parameters commonly measured as part of various champion tree programs and documentation efforts. Other commonly used parameters, outlined in tree measurement, include height, girth, and volume. Additional details on the methodology of tree height measurement, tree girth measurement, and tree volume measurement are presented in the links herein. American Forests, for example, uses a formula to calculate Big Tree Points as part of their Big Tree Program that awards a tree 1 point for each foot of height, 1 point for each inch of girth, and ⁠1/4⁠ point for each foot of crown spread. The tree whose point total is the highest for that species is crowned as the champion in their registry. The other parameter commonly measured, in addition to the species and location information, is wood volume. A general outline of tree measurements is provided in the article tree measurement, and more detailed instruction in taking these basic measurements is provided in "The Tree Measuring Guidelines of the Eastern Native Tree Society" by Will Blozan.

Data on greatest crown spread is somewhat limited as this parameter is not measured as frequently as are tree height and trunk girth. The largest recorded is the "Monkira Monster" (Eucalyptus microtheca) located at the Neuragully Waterhole in southwestern Queensland, Australia, which measured 239 feet in 1954. A raintree (Albizia saman) in Venezuela was measured to have a crown spread of 207 feet in 1857. It reportedly is still living, but in poor health. A University of Connecticut site suggests that in the wild they may have crown spreads up to 80 meters. Robert Van Pelt measured a crown spread of 201 feet of a kapok tree (Ceiba pentandra) at Barro Colorado Island, Panama, in 2003.

The average crown spread is the average of the lengths of longest spread from edge to edge across the crown and the longest spread perpendicular to the first cross-section through the central mass of the crown. Crown spread is taken independent of trunk position. Spread should be measured to the tips of the limbs, not to "notches" in the crown shape, and at approximately right angles from each other.

The surveyor locates the point on the ground immediately below the branch tip on one end of the measurements and marks that position. He then moves to opposite side of the crown and locates the point under that branch tip. The spread along that line is the horizontal distance between those two positions. On steeply sloping ground (over 15 degrees) the taped distance between the two points can be corrected to a true horizontal by using basic trigonometry: horizontal distance = cos(inclination) × slope distance. The help of an assistant or the use of a laser rangefinder can greatly speed this process. When using a laser rangefinder, as in measuring tree height, several points on the far edge of the crown can be explored to find the furthest point. A laser rangefinder is also useful for measuring crown spread where one side of the crown is not easily accessible, such as a tree growing on a cliff side or other barrier.^{[citation needed]}

When using the spoke method, four or more measurements are taken from the outer dripline of the crown to the side edge of the trunk. The distance to the side edge of the trunk is for all practical purposes equal in length to the distance to the center of the trunk. If the measurement from the dripline of the crown to the side edge of the trunk is not level, then the measured length must be converted to a horizontal distance.

If the slope angle is less than 10 degrees the difference between the horizontal distance and the measured length will be less than 1.5% for slope distances less than 100 feet. These individual spoke lengths are averaged and this average is equal to half the average crown spread. The more spokes measured in the process, the more accurate the characterization of the average crown spread.

This is the preferred method of canopy researchers and is probably the most accurate, and can also be used to quantify crown area. On large trees it can be accomplished quickly with a laser rangefinder.