Editorial standard
Every Lumber Tally calculator is expected to answer a defined shop question, identify its input units, expose the governing formula, and state the construction assumptions that can change the result. We prefer a narrower calculator with checkable math over a broad estimator that hides unsupported assumptions. Articles and examples are written for this site and are reviewed against the calculator implementation rather than copied from a supplier chart.
Board feet
Imperial: thickness in inches × width in inches × length in feet × quantity ÷ 12. A 1 × 8 × 8 board equals 5.333 board feet. Metric dimensions are converted from cubic millimeters using 1 board foot = 2,359,737.216 mm³.
The imperial formula works because a board foot is 144 cubic inches. A length entered in feet is multiplied by 12 to convert it to inches, and the combined expression simplifies to division by 12. The metric conversion uses the exact relationship between inches and millimeters rather than a rounded shop approximation.
Waste allowance is applied after the base batch total: planned board feet = base board feet × (1 + waste percentage ÷ 100). Estimated material cost uses the planned total when an allowance is enabled. Individual rows retain precision until the batch is combined, which prevents rounding every board upward or downward before the total.
Nominal and actual dimensions
The calculator accepts the dimension the user enters; it does not silently convert a nominal 2×4 into 1.5×3.5 inches. This is deliberate because hardwood yards, construction-lumber sellers, slab dealers, and project cut lists use different conventions. The page explains when rough, nominal, or actual dimensions are appropriate, and the user remains responsible for matching the supplier's tally method.
Rough-lumber purchase planner
Each finished part is first measured as finished thickness × finished width × finished length × quantity ÷ 144, with all dimensions in inches. Its rough blank is measured as selected rough thickness × (finished width + width cleanup) × (finished length + end trim) × quantity ÷ 144. The difference between those two volumes is reported as the dimensioning difference.
Selection contingency is applied to the combined rough-blank volume, not the finished volume: purchase BF = rough-blank BF × (1 + contingency percentage ÷ 100). This separation prevents milling stock and defect risk from being hidden inside one unexplained percentage. The estimate does not perform two-dimensional cutting optimization or guarantee that available board geometry can yield every part.
Lumberyard tally and invoice comparison
Exact mode uses the standard imperial volume formula with quarter thickness expressed in inches, measured width in inches, and length in feet. Rows retain their full precision until they are summed. NHLA estimate mode follows the measurement sequence in the NHLA hardwood rules: fractional standard length is dropped, each board's surface measure is rounded to a whole foot, exact half-foot cases alternate upward and downward, and the rounded surface measure is multiplied by standard thickness. This option remains an estimate because a seller's contract or local practice may use another method.
Material cost equals the selected tally total × quoted price per BF. Tax is applied to the material subtotal only; user-entered milling or delivery fees are added afterward because local tax treatment varies. Invoice difference equals dealer invoice BF minus the selected comparison basis. A displayed difference is not labeled an error because supplier-specific rounding, nominal thickness, width measurement, and length increments can legitimately produce another tally.
Drawer boxes
Finished outside width equals opening width minus total side clearance. Finished outside depth equals opening depth minus rear clearance. With front and back between full-length sides, their length equals outside width minus two side thicknesses.
An applied bottom is reduced by the selected edge setback. A captured bottom entering grooves in all four box parts equals the inside dimension plus twice the groove depth. Slide presets are examples only; the exact hardware installation sheet controls.
Inputs are validated to reject a result when the selected clearances or material thicknesses consume the available opening. Bottom dimensions are derived from the finished box geometry, not independently rounded part sizes. The tool does not infer load capacity, joinery strength, screw selection, solid-wood movement, or hardware compatibility.
Drawer-box test cases
Tests cover applied and captured bottom modes, front-and-back parts fitted between sides, and changes to material thickness. A representative captured-bottom case checks that the panel enters both opposing grooves by exactly the entered groove depth. Warnings remain visible when a preset is only an example and a manufacturer sheet must control.
Cabinet doors
Overlay size adds the overlay at both edges. Inset size subtracts the clearance at both edges. For paired doors, the center reveal is removed before dividing the covered width by two. Cope-and-stick rail length and panel dimensions include the entered groove depth; tooling profiles and solid-panel movement must be verified in the shop.
For a single overlay door, finished width = opening width + left overlay + right overlay. The current interface uses equal overlay values on both sides, so that becomes opening width + 2 × overlay. For an inset door, finished width = opening width − 2 × edge clearance. Height follows the same rule. A paired layout calculates the total covered width first, subtracts one center reveal, and then divides by two.
The Shaker cut list assumes full-height stiles and rails between the stiles. Rail cut length includes two groove engagements. Center-panel dimensions represent the frame opening plus groove engagement, before any project-specific movement deduction. Because cutter profiles vary, this output is a starting geometry rather than a claim that every rail-and-stile system uses identical shoulders or tongue lengths.
Equal spacing
Available space equals total span minus the combined item widths. Flush-end layouts divide by item count minus one; equal-end layouts divide by item count plus one. A single flush item has zero gaps. The display rounds shop measurements to the nearest 1/32 inch while retaining decimal precision internally.
The result describes clear space between item edges. On-center spacing is one clear gap plus one item width when all item widths are equal. A layout is rejected when the combined item widths exceed the span. The preview limits the number of visual elements for readability, while the numerical result remains based on the full entered count.
Board and batten
The board-and-batten layout is a specialized flush-end spacing problem. Both outer battens sit flush with the measured span. Clear gap = (wall span − batten count × batten width) ÷ (batten count − 1). On-center spacing = clear gap + batten width. Position values are cumulative from the same control edge so rounding one displayed gap does not compound across the wall.
Vertical linear feet equal batten count × batten height, with the entered waste factor applied afterward. The estimate intentionally excludes top rails, base rails, caps, returns, and trim around openings because those elements require separate dimensions.
Units and rounding
Calculations are performed with decimal numbers. Human-readable inch fractions are display values rounded to the nearest 1/32 inch and are not fed back into later calculations. Metric values are converted at defined boundaries and are checked against equivalent imperial examples. Currency output is a planning estimate and does not add tax, delivery, tiered pricing, minimum order quantities, or supplier-specific rounding.
Input validation and edge cases
Release checks include empty or zero quantities where they are meaningful, negative-space layouts, one-item spacing, paired-door center reveals, unrealistic clearances, and both applied and captured drawer bottoms. A zero board quantity contributes zero volume rather than forcing an artificial minimum. A no-fit spacing layout returns a warning rather than a negative gap presented as usable.
Validation cannot determine whether a wall is square, a board contains a defect, a slide model matches a preset, or a building-code rule applies. Those limits are stated beside the relevant calculator. The safest workflow is to calculate, independently check one worked example, measure the actual material, and make a test piece before committing a full batch.
Test coverage
Release checks include known worked examples, unit-conversion equivalence, zero quantity, no-fit layouts, one-item layouts, paired-door reveals, and both applied and captured drawer bottoms. Results are not rounded before totals are calculated.
Automated tests are run before a production release. They verify numerical outputs and confirm that every public calculator and trust page renders successfully with expected titles, canonical URLs, and navigation links. Tests reduce regressions but do not replace real-world verification against supplier rules or manufacturer instructions.
Corrections policy
Reproducible errors are corrected in the formula and accompanied by a regression test when possible. Clarifications that do not change the numerical result are added to the relevant guide. To report an issue, use the Contact page and include the exact inputs, units, actual result, and expected result.
Last reviewed: July 27, 2026.