Log cutting plan: how to build an efficient layout manually vs. with software

Building an efficient cutting plan is one of the most impactful decisions a sawmill operator makes every day. For each log that arrives in the yard, there is a set of questions: how many pieces fit? In what position? Which dimensions make the best use of this diameter?

The difference between a well-calculated layout and an improvised one can be 5 to 12 percentage points in yield — which in an operation of 200 logs per day represents hundreds of additional pieces without purchasing a single extra log.

In this article you will learn how to build a cutting plan manually, step by step, understand the limits of that process, and see how software solves the same problems with far greater speed and precision.

What is an efficient cutting plan?

An efficient cutting plan is the arrangement of rectangular pieces within the circular cross-section of a log that maximizes the volume of usable wood, while respecting three physical constraints:

1. No piece can exceed the log's circumference (or the defined safety margin)
2. Pieces cannot overlap
3. The space between pieces must account for the saw blade's kerf width

The goal isn't just to fit the largest number of pieces, but to maximize the total volume of usable lumber. One large piece recovers more volume than many small ones. A mixed layout, calibrated to the exact diameter, typically outperforms any fixed pattern.

How to build a layout manually (step by step)

The manual process is feasible for sawmills working with one or two fixed dimensions and relatively uniform diameters. Here is how to do it correctly:

Step 1: measure the diameter precisely

Use calipers or a tape measure to record the diameter at the log's entry point. Write down the exact value without rounding. A difference of just 2 cm in diameter can change how many pieces fit in the layout.

If the log is tapered (different diameter at each end), use the smaller diameter as reference to ensure all pieces come out clean along the full length.

Step 2: calculate the effective diameter

Subtract the safety margin from the gross diameter. The margin compensates for natural wood imperfections and ensures clean-edged pieces:

Step 3: position the largest pieces in the center

At the log's central axis, you have the greatest available width. Begin by positioning the largest dimension pieces in the center, stacked vertically. Calculate how many fit within the available height, summing thicknesses plus the kerf between each cut.

Example: 300 mm effective diameter, 4 mm kerf, 75x50 mm pieces:

• Center block: 300 mm width fits 3 columns of 75 mm (225 mm total) with lateral clearance
• Stacked height: 5 pieces x 50 mm + 4 kerfs x 4 mm = 250 mm + 16 mm = 266 mm (fits within 285 mm)
• 5 pieces x 3 columns = 15 pieces in the central core

Step 4: fill the edges with smaller pieces

After positioning the central core, analyze the remaining edge space. The log's curvature reduces available width as you move away from the center axis. Use the geometric formula:

For a log with radius r, the available width at height h above or below center is: 2 x sqrt(r² - h²)

In practice, calculate for 2 or 3 positions and determine which smaller pieces (or pieces rotated 90°) fit in the remaining lateral space.

Step 5: calculate yield and compare alternatives

Sum the volume of all positioned pieces and divide by the total log volume:

Yield = (sum of width x thickness x length per piece) / (PI x radius² x log length)

Try at least 2 layout variations (for example, swapping the center dimension or rotating lateral pieces) and compare yields before setting the cutting standard.

The limits of the manual process

The method above works, but has constraints that impact result quality:

1. Limited number of tested variations

An operator can test at most 3 to 5 different layouts for a given diameter. An optimization algorithm tests dozens of combinations in fractions of a second, including non-obvious arrangements an operator would rarely consider.

2. Calculation errors at the edges

Manual calculation of circular geometry is prone to rounding errors. A piece positioned 2 mm beyond the circle boundary produces a bark-edged piece that will be rejected. Software performs geometric verification with sub-millimeter precision for all vertices of every piece.

3. Difficulty with mixed dimensions

When you need to combine two or three different dimensions in the same layout (for example, large beams in the center and battens on the edges), the fitting problem becomes combinatorially complex. Calculating this manually for each diameter is impractical in daily sawmill operations.

4. Recalculation with every diameter change

If your sawmill processes logs with varying diameters (very common), the layout must be recalculated for each range. Keeping manual tables updated for 10 or 15 different diameter ranges is laborious and frequently produces outdated tables.

How software solves the same problem

Cutting optimization software solves exactly the same steps as the manual process, but automatically and with far more tested alternatives:

When the manual process still makes sense

Manual layout calculation still has value in specific situations:

• Sanity check: understanding the manual process helps operators validate whether the software's output makes geometric sense
• Emergency situations: when the system is unavailable and a basic layout is needed quickly
• Single dimension, fixed diameter: if the operation always processes the same log with the same piece, a manually calculated layout recorded once can work well
• Training: teaching the manual process to new operators builds intuition for cutting geometry, making them better software users

Conclusion

Building a cutting plan manually is possible, and it is worth understanding how it works. But in the day-to-day routine of a sawmill processing dozens or hundreds of logs with varying diameters and mixed dimensions, the manual process leaves yield on the table.

Software does not replace the experienced sawyer's judgment. It eliminates the calculation work and frees that judgment for where it truly matters: reading the wood, calibrating equipment, and ensuring final product quality.