About & Methodology

Economic & Lumber Prices

All lumber price data on ThePlotMetrics is derived from the FRED Series WPU0811 (Producer Price Index by Industry: Softwood Lumber) maintained by the Federal Reserve Bank of St. Louis. Raw index values are converted to real-dollar estimated costs using a proportional model calibrated against pre-pandemic retail averages. Our baseline index of 240.0 approximates the 2019 softwood lumber PPI average. Our baseline reference formula is:

This methodology provides a repeatable, verifiable proxy for tracking how wholesale PPI movements affect out-of-pocket costs at lumber yards and home improvement stores across the United States.

Engineering & Lumber Cut Lists

Our lumber calculators apply actual nominal construction dimensions (e.g., a 2×6 board measures 1.5″ × 5.5″ in reality) and use zero-waste matrix optimization algorithms to minimize offcuts. Cut lists account for kerf width, standard lumber lengths, and structural best practices to ensure every board recommendation is both mathematically optimal and buildable with common tools.

Soil Volume & Compaction Math

Every soil calculator on the platform uses the geometric volumetric formula V = L × W × D as its foundation, then applies a standard 10 % compaction and natural settling buffer to account for the volume reduction that occurs after the first watering. This ensures that gardeners order enough material to fill their beds to the desired depth after the soil has had time to settle — a detail often missed in simpler calculator tools.

Agronomic & Crop Spacing Standards

The Grid Planner and Crop Rotation tools apply biological principles from the Solanaceae, Fabaceae, Brassicaceae, and other plant families — enforcing recommended spacing, companion-planting compatibility, and rotation intervals that prevent nutrient depletion and disease buildup. Densities follow the established Square Foot Gardening methodology, adapted for raised-bed configurations typical of the U.S. home garden.