Scaling logs comes in handy while asking for estimations from a carpenter. It helps us negotiate better deals and understand the return on investment. Look before you leap, and you’ll be safe.Disclaimer: Scaling logs online is for estimations only, results are not always accurate.
Suppose you are looking to buy or sell timber. In that case, you should probably know your way around the different calculation methods used for it. While height and diameter play their respective roles in these calculations, the timber volume plays the most important role of them all.
This is because timber volume determines the value or quality of the timber itself. Knowing the timber value is crucial for both parties: buyers will see the amount they should offer, and sellers will see the amount they should receive for the wood. Timber calculation required charts after charts of numbers in the past, but now, with the help of online calculators, the process has become a lot faster and simpler.
What is Timber
Timber is fundamentally wood. They may be standing timber, which are living trees that are yet to be harvested, felled trees in the process of being cut, or even processed timber shaped into beams, planks, etc. Any wood available to be turned into different kinds of wood products is essentially timber.
We need a log weight calculator and log volume calculator for different uses. Online calculators are useful, but sometimes we need to walk the walk. Let me help you understand the math behind timber weight and volume calculation methods. Feel free to use our online calculator for quick estimations. Log scaling refers to log volume calculation. Commonly used log volume calculation scales are:
- Doyle Scale
- Scribner Scale
- International Scale
Log Weight Calculator
Steps of Log Weight Calculation
Identify the species of the tree.
Measure the diameter (inches) of the timber using a diameter tape or logger tape.
Measure the length/height (feet) of the timber using a clinometer or Biltmore stick.
Enter your diameter and length values in their respective boxes.
Specify the total number of logs you want to measure.
Log Volume Calculator
Steps of Log Volume Calculation
Use tree calipers to record the small end diameter (inches) of the log.
Use a graduated tape or logger tape to measure its length (feet).
Specify the number of similar sized logs you want to measure.
Cylindrical Formula for Log Volume Calculation
This formula is for those scalers who want a quick and easy way to measure the log volumes. Even though fuelwood and pulpwood volumes can be calculated, the cylindrical formula should not be used for all kinds of timbers, especially hardwood timbers.
Formula: V=π×r^2×l where, V = volume, r = radius or diameter, l = length.
Cone Formula for Log Volume Calculation
The cone formula is a hack. Measure the diameters on both ends along with its length. Use your values to calculate the volume using the cone formula.
Formula: V=π×r^2×l/3 where, V = volume, r = radius or diameter, l = length.
Again, it is better to use cone formula for softwoods rather than hardwoods.
JAS Scale for Log Volume Calculation
The small end diameter is considered for logs less than 14 cm, and for those more than equal to 14 cm, diameters of both ends have to be taken. Volume values are taken as three significant figures.
For logs less than 6m long:
Formula: V=(D^2×l)/10,000, Where V = volume, D = diameter, l = length.
For logs equal to greater than 6m:
Formula: V=((D+[l’-4])^2)/(l/1000), Where V = volume, D = diameter, l = length, l’ = length rounded down to nearest whole number.
Log Scales and Log Rules
Log scaling is done to get a rough idea of the measurements of the logs. This requires log rules to be applied. Log rules use standard units of measurement to determine the factors of a log. Together they establish:
- Quality of Wood.
- The estimated value of the Log.
- Approximate Log Volume.
- The predicted amount of timber obtained from the set number of saw logs.
- D = Diameter of the small end
- d= Diameter at the middle of the bark
- BF= Board feet volume
- CF= Cubic feet volume
- L= Nominal log length
Types of Log Scaling Rules
No log is evenly shaped; hence different log rules use different methods to find their estimated volumes. Bear in mind, many log rules exist, but the more commonly used and accurate ones are explained below.
Doyle Log Rule
This rule is often applied to scale or determine the value of hardwood logs. It uses the log length, diameter, how much the log shrinks, and how much sawdust is produced while processing to estimate the volume.
On the other hand, it does not measure the taper (the log reduces in size as it keeps growing above the ground) of the log properly, nor does it take edges into account the right way. Hence, it under-scales small logs and over-scales long logs. Yet, because of its vast use, the measurements it provides have become the standard for scaling hardwoods in some places of the world.
Doyle Log Rule Formula
Log Volume (in board feet) = ((D-4)^2 L)/16
Scribner Log Rule
Uses tables of volume, length, and log yield (usable timber) to demonstrate a practical view of the rule. It may be useful in the case of logs that are 16-feet long but not for logs that are longer than that. This is because it does not take taper into account and hence the value of the volume is lower than the actual value.
Scribner Log Rule Formula
Log Volume (in board feet) = (0.79D^2-2D-4)L/16
International ¼ – inch Log Rule
The ¼ inch here refers to the saw kerf (the amount of log thickness the saw blade cuts) allowed by the rule. This rule is used to estimate how much of the log is wasted during processing. The waste is the portion of the wood that is lost as unusable wood, sawdust, etc. This rule also takes taper into account.
International ¼ – Inch Log Rule Formula
BF=(0.199D^2-0.642) (FOR 4 foot length)
The formulas for international ⅛, 1/12, 1/16, and 1/20 inch Log Rules are given below respectively:
- BF=(0.398D^2-1.086D-0.27) (FOR 8 foot length)
- BF=(0.59D^2-1.330D-0.72) (FOR 12 foot length)
- BF=(0.796D^2-1.375D-1.23) (For 16 foot length)
- BF=(0.995D^2-1.221D-1.72)(FOR 20 foot length)
Best Methods of Scaling Logs
Board-Foot Log Scaling Method
This commonly used method gives a rough estimation of the volume (in board foot) of the total amount of timber that can be cut from a log. A log rule has to be applied to scale the log.
Weight Scaling Method
This method requires a truck to be weighed with the loaded logs first. Then, the truck is weighed again to subtract its value from the truck full of logs. This subtracted value is the weight of the timber in total. Later, it is converted to board of cubic feet. The advantages of using this method include quick completion, lower scale cost, and log handling.
However, this method isn’t always accurate, accuracy depends on log quality, diameter, and length. So, landowners may end up paying the same amount for more logs with low diameters and lengths with the same weight as fewer logs with better diameters and lengths.
Electronic sawmill devices such as volume scanners measure log length, diameter, and taper to find out the volume. They are far more precise than the previously mentioned methods. So much so that they run on their own in large timber processing factories.Note: Electronic volume scanners are quite pricey. However, they are a good investment for large scale operations.
Best Methods of Measuring Timber
Follow the same system of measurement for calculation. Whether the imperial system or metric system, stick to one while taking measures. It is advised to use-
- Meters to measure the length of timber.
- Centimeters to measure the diameter.
- Tonnes to measure weight.
- Cubic meters to measure the volume
If you measure in centimeters, make sure to round your decimals to the nearest whole centimeter. For example, 7.67 cm becomes 8 cm.
|Imperial System Measurement Chart|
|1 foot = 12 inches|
|1 yard = 3 feet = 36 inches|
|1 mile = 1750 yards = 5280 feet|
|1 pound = 16 ounces|
|1 stone = 14 pounds = 224 ounces|
|Metric System Measurement Chart|
|1 centimeter = 10 millimeter|
|1 meter = 100 centimeter = 1000 millimeter|
|1 kilometer = 1000 meter|
|1 kilogram = 1000 gram|
|1 ton = 1000 kilogram|
Required Tools to Measure Standing Timber
Measures the diameter breast height (DBH) of a tree. It is small and easy to carry.
Wrap the tape around the circumference or chest height of the tree, approximately 4.5 ft above ground level, to get the timber’s diameter. Make sure the right end of the tape is on top of the left end.Note: If a tree or log has a DBH of less than 7 cm, it has no volume.
This also measures the DBH of a tree but gives a more accurate value. They are heavier and cannot be bent.
At 4.5 ft from ground level, place the two points of the caliper on either side of the timber, perpendicular to the side of the tree. The diameter on the caliper scale is your first reading. Repeat the process twice at right angles of each other. Calculate its mathematical average or mean (two of your values divided by 2), and you will have a precise DBH of the tree.Note: If you do not have a diameter tape or a tree caliper, use a measuring tape to find out the DHB. Measure the circumference and divide your value with pi, whose symbol on the calculator is π. However, the reading on the tape will not be as accurate as the ones listed above.
This is used to measure the total height or merchantable height of a tree. Merchantable height is the usable tree’s length starting from its stump to the marketable point of the tree. If the stem or trunk is too thin to be sold, it is left out of the merchantable height.
- Stand at a distance from the tree, which should be more than equal to its height.
- Measure your distance from the tree and the height at which the clinometer will be placed from the ground.
- Look through the clinometer with one eye and fix your other eye on the tree.
- Align the crosshair (a fine piece of thread used for line reference) of the clinometer to the top of the tree.
- Read the value on the clinometer’s percent scale, which is the tree’s height given as a percentage. Let’s say your reading is 50%; this means the tree’s height is half the distance you are from it.
- Calculate the height using the formula:
The age and growth rate can be checked using an increment borer. Here, we are interested in the growth rate as wood densities vary with them. In some hardwoods, for example, a fast growth rate indicates denser wood quality.
A small straw-like sample is collected from the bark to the center of the tree, which is later examined to determine its growth rate and hence its density.Note: Although the sample taken out is tiny, decay can still form in the trunk. As a result, only one bore every six years is allowed. It is also mandatory to put the sample back inside the tree’s hole once the work is done.
Also known as cruiser stick, is a tool that looks like a long ruler used to measure the volume, height, and diameter of the tree or log. It has a conversion chart on its back.
Measuring the diameter using Biltmore Stick
- Hold out your cruiser stick horizontally.
- Make sure it is at least 4.5 ft from the ground and 25″ from eye level.
- Put the back of the stick against the tree.
- Align the left side of the tree with the starting point or zero inches of the stick.
- Carefully shift your eyes (do not move head) to the end of the trunk. The point at which the stick crosses the trunk is your diameter reading.
Measuring the Total or Merchantable Height using Biltmore Stick
- Stand at least 100 ft from the tree you want to measure.
- Hold the stick out vertically, 25″ from eye level.
- For total height, align the stick with the ground and align the stick with the stump for merchantable height.
- Carefully shift your eyes (do not move head) until they meet the tree’s top or merchantable height.
- The closest log mark is the total height or merchantable height.
Measuring the Volume of the Log or Tree using Biltmore Stick
- Find the diameter of the tree as per the scale given at the back of the stick.
- Find the height in 16-foot logs from the left side of the table given.
- Trace along with the table until you reach the box where the corresponding height meets the corresponding diameter.
- The number you will arrive at is your board foot volume. Board foot is the unit of volume.
Required Tools to Measure Felled Timber
Used in forestry for making land measurements of felled timber. They are sturdy, self-retracting, and have a quick-release nail attached to the end.
Poke your fingernail inside your chosen log and move the distance you need to measure the log’s diameter or length. Once done, lightly pull the nail, and it will retreat to its place.Note: Logger tapes do not work well in muddy areas.
Plastic Graduated Tape
Place the tape against the log and measure it. Repeat if the log goes beyond the length of the tape. Remember to mark the point at which you begin again.
Once a plot is sampled or radius is determined, an angle gauge can be used to measure which trees fall inside and outside the chosen area of land. It comes with a chain to help you hold it at a certain distance from you.
Stand in the center of the plot and hold the angle gauge at the set distance from eye level. Then count the trees that are larger in width than the angle gauge. If they are larger, they fall within the plot. If they do not fill the opening of the gauge, they fall outside the plot.Note: A glass wedge prism has the same use as the angle gauge, except they are not fit to determine whether denser trees fall in or out of the sampled plot.
Types of Timber
First and foremost, timber has two main classifications: hardwood and softwood. A fundamental distinction between the two is that the former is heavier while the latter is lighter. While they are typically ‘harder’ and ‘softer’ as their name suggests, it is not always the case. Hence, their measurements are taken differently. Here’s a fact: 80% of the world uses softwood, mainly because they are less expensive and easier to work with.
Under the aforementioned categories, we have many kinds of timber such as- oak, teak, and mahogany, essentially hardwoods and pine, spruce, and fir, which all fall under softwoods. Apart from these, various other timber types have their pros and cons.
Uses of Timber
Timber is one of the most versatile and frequently used raw materials in the world. Trees are everywhere, and one of the oldest renewable resources. Therefore, it is readily available whenever needed. Consequently, it has a long list of uses around the world, and the following are some of them:
- Housing structure (Always a better option against bricks in earthquake-prone areas)
- Source of fuel (40% of the world’s timber is used as a fuel source in the end)
- Paper (Timber waste as minuscule as sawdust can be used to make paper)
- Musical Instruments (Timber is crucial to building the right soundboards and boxes)
- Energy sources (Old wood can be converted into an eco-friendly source of heat or electricity)
As established before, timbers can come in many shapes and forms: softwood, hardwood, plane, rough, tapered, etc. Hence, there is a lot to consider before taking its measurements. To review quickly:
- Make sure to use the appropriate tool where necessary for felled or standing timber
- Use log scales and rules to get an estimated idea of your measurements
- Choose your calculation method wisely- many can calculate volume but do not settle for the simpler ones, especially in the case of hardwoods, just because they are easier to use
If you follow the rules and methods accordingly, you will be going into business well-informed. As they say, an expert is a man who knows just that much more about his subject than his associates. Dare to be that person and maximize your utility to its fullest.
Now that we understand how to use the essential tools and log rules to calculate required variables, you can use different calculation techniques for various timber types. It would be much easier for you to use our online log weight calculator and log volume calculator. Scaling logs have never been easier.