Calculate Income for Logs in Scribner Board Feet
Estimate board foot volume and gross log income using the Scribner rule, log dimensions, market price per thousand board feet, and a quality adjustment.
Enter your log dimensions and market price, then click Calculate Income.
Expert Guide: How to Calculate Income for Logs Using Scribner Board Feet
When landowners, foresters, buyers, and small sawmill operators need a quick estimate of log value, one of the most common methods in western North America is to calculate volume in Scribner board feet. Once the board foot volume is known, estimated log income becomes straightforward: multiply total volume by the market price per thousand board feet, then adjust for species, quality, defects, hauling assumptions, or local market discounts. If you want to calculate income for logs in Scribner board feet accurately, the key is understanding what the Scribner rule does, what it leaves out, and how to apply it consistently.
The Scribner rule is a log scaling rule designed to estimate how many board feet of lumber can be sawn from a log. A board foot is a standard lumber measurement equal to a piece of wood that is 12 inches long, 12 inches wide, and 1 inch thick. That means 1 board foot = 144 cubic inches. In timber marketing, prices are often quoted per MBF, which means one thousand board feet. So if your logs scale to 5,400 Scribner board feet and the market is paying $650 per MBF, your gross revenue before deductions is 5.4 x $650 = $3,510. That basic framework is what this calculator helps you estimate.
What the Scribner Rule Measures
The Scribner rule estimates lumber yield from a log based primarily on small-end diameter and log length. In practical field use, a scaler often measures the diameter inside bark at the small end and applies a Scribner scale table. For fast estimating, a commonly used approximation is:
Scribner board feet ≈ ((D – 4)² x L) / 16
Where D is small-end diameter inside bark in inches, and L is log length in feet. If diameter is 4 inches or less, the estimated Scribner volume is effectively zero.
This formula is not a substitute for an official mill scale or a state-certified scaler, but it is a useful planning tool for comparing harvest scenarios, estimating sale value, and creating rough budgets before trucking and scaling. Many woodland owners use it to answer questions like: “If I have twelve 16-foot Douglas-fir logs averaging 18 inches on the small end, roughly what is my income at today’s mill price?”
How to Calculate Income Step by Step
- Measure the small-end diameter inside bark. This is critical because volume changes quickly with diameter. A 2-inch change can make a big difference in total board feet.
- Measure merchantable log length. Common lengths include 8, 12, 16, and 20 feet, although actual merchandizing depends on your buyer and mill specifications.
- Count the logs. Multiply the per-log Scribner estimate by the number of logs with similar dimensions.
- Apply market price per MBF. Divide total board feet by 1,000 and multiply by the log price.
- Adjust for quality or species. Straight, sound, premium species often bring more. Sweep, rot, checking, or mixed species often bring less.
For example, assume one 16-foot log has an 18-inch small-end diameter. Using the estimator:
((18 – 4)² x 16) / 16 = 196 board feet per log
If you have 12 such logs, total volume is:
196 x 12 = 2,352 board feet
At $650 per MBF, base gross value is:
2.352 x $650 = $1,528.80
If your species and quality adjustments combined equal 0.95, the adjusted gross estimate becomes:
$1,528.80 x 0.95 = $1,452.36
Why Diameter Matters So Much
One of the most important lessons in log valuation is that diameter has a squared effect in the quick Scribner estimate. That means value often rises much faster with diameter than with length alone. A modest increase in small-end diameter can increase gross income substantially, especially when many logs are involved. This is one reason forest management decisions around thinning, rotation age, and stand quality can materially affect revenue at sale time.
| Small-End Diameter | Length | Approx. Scribner BF per Log | Volume in MBF | Gross Value at $650/MBF |
|---|---|---|---|---|
| 12 inches | 16 feet | 64 BF | 0.064 | $41.60 |
| 14 inches | 16 feet | 100 BF | 0.100 | $65.00 |
| 16 inches | 16 feet | 144 BF | 0.144 | $93.60 |
| 18 inches | 16 feet | 196 BF | 0.196 | $127.40 |
| 20 inches | 16 feet | 256 BF | 0.256 | $166.40 |
The table above uses the fast estimating formula and shows how quickly gross value climbs as small-end diameter increases. In a truckload of logs, these differences become significant. That is why buyers inspect taper, sweep, breakage, and defects carefully: small changes in recoverable lumber can translate into meaningful dollars.
Length Matters Too, But Usually More Linearly
In the simplified formula, length changes volume on a roughly linear basis. If diameter stays constant and length doubles, estimated Scribner volume approximately doubles as well. However, in real logging operations, longer logs may not always maximize value. Mill specs, trim allowance, defect placement, transport rules, and merchandising strategy all matter. Sometimes two shorter logs may outperform one longer log if a defect can be isolated and removed.
| Diameter | Length | Approx. Scribner BF | Value at $650/MBF | Value at $850/MBF |
|---|---|---|---|---|
| 18 inches | 8 feet | 98 BF | $63.70 | $83.30 |
| 18 inches | 12 feet | 147 BF | $95.55 | $124.95 |
| 18 inches | 16 feet | 196 BF | $127.40 | $166.60 |
| 18 inches | 20 feet | 245 BF | $159.25 | $208.25 |
Important Limits of a Scribner Income Estimate
Even a strong estimator is still just an estimate. Real-world timber income often differs from a simple board foot calculation because several factors can change both scale and price:
- Defects: Rot, shake, crook, excessive sweep, cat faces, and breakage can reduce scaled volume or downgrade the log.
- Bark thickness and taper: Diameter inside bark must be measured carefully. Overestimating usable wood inflates income projections.
- Mill specifications: Mills may pay on Scribner, Doyle, International 1/4-inch, weight, or cubic measures depending on the region.
- Species premiums: Certain species or grades may carry stronger prices, especially where appearance lumber or specialty products are in demand.
- Season and local demand: Prices can move with export activity, mill shutdowns, construction cycles, and freight costs.
- Harvest and trucking deductions: A gross value estimate is not the same as net income to the landowner.
For this reason, you should treat a calculator like this one as a planning and comparison tool rather than a formal timber appraisal. It is very useful for screening opportunities, evaluating stand treatments, or preparing for conversations with buyers, loggers, and consulting foresters.
Gross Revenue vs. Net Timber Income
A common mistake is to calculate gross log revenue and assume that is take-home income. In reality, net income may be lower after deducting:
- Harvesting or logging contractor costs
- Road work and landing preparation
- Trucking charges
- Scaling and administrative fees
- Broker or consulting forester commissions
- Reforestation or slash treatment obligations
If your estimated gross value is $20,000 and your total operational costs are $9,000, then your rough pre-tax net becomes $11,000. That difference is why scale estimates should always be paired with a cost sheet if you are evaluating a timber sale.
Using the Calculator More Effectively
To get better estimates, group logs by similar size instead of averaging everything into one number. For example, calculate separate batches for 14-inch, 18-inch, and 22-inch logs, then add the totals together. This is more accurate because the Scribner estimate is sensitive to diameter. Also consider entering a conservative quality adjustment when your logs have visible sweep, butt flare, or defect risk.
If you are managing a woodland property, this kind of calculator can also support strategic decisions such as:
- Comparing immediate harvest against delayed harvest
- Evaluating thinning revenue potential
- Estimating salvage value after storm or fire damage
- Budgeting small private timber sales
- Preparing preliminary figures for estate, tax, or management planning
Scribner Compared with Other Log Rules
The Scribner rule is popular, but it is not universal. In some regions, buyers may use other scaling methods. That matters because the same logs can produce different reported board foot volumes under different rules. If you are comparing bids from different buyers, always verify the scaling rule and whether deductions are included.
In general terms, the Scribner rule tends to work best as a practical estimate for medium and larger sawlogs, while smaller logs may show more variation between rules. If one mill quotes a higher dollar figure but uses a more conservative scaling basis, the apparent premium may disappear after conversion. Apples-to-apples comparison is essential.
Authoritative References for Timber Measurement and Forest Economics
For official measurement guidance, extension references, and market context, review these sources:
These institutions publish practical materials on log scaling, timber sale planning, forest product measurement, and woodland economics. If you are preparing for an actual sale, your best next step is often to combine your own estimate with a professional opinion from a consulting forester or mill buyer in your region.
Best Practices Before You Rely on an Income Estimate
- Measure multiple logs, not just one representative sample.
- Use diameter inside bark if possible.
- Separate premium and lower-grade logs into different groups.
- Confirm whether the local market quotes in Scribner, Doyle, or another rule.
- Ask buyers about trim, defect deductions, and trucking responsibilities.
- Estimate both gross and net revenue.
- When values are substantial, get a professional timber appraisal.
Ultimately, to calculate income for logs in Scribner board feet, you need three essentials: accurate dimensions, a reasonable market price, and realistic quality assumptions. The calculator above gives you a fast, field-friendly estimate of gross income and visually compares the revenue effect of different log lengths. Used correctly, it can help you make better harvesting, marketing, and woodland management decisions with much greater confidence.