Construction calculators

Board Foot Calculator

Updated Sep 26, 2026 By Infinity Calculator
Rate Formulas Sources
Enter roughsawn thickness in quarters (e.g., 4/4, 5/4, 8/4) or decimal inches.
Please enter a valid number or fraction (e.g., 6 1/2 or 6.5).
Please enter a valid number or fraction (e.g., 6 1/2 or 6.5).
Please enter a valid number or fraction (e.g., 8 or 10.5).
Number of identical boards.
Enter price per board foot to calculate total cost.
Results
Board Feet (per board)
4.00 BF
Total Board Feet
4.00 BF
Quarterized Thickness
4/4 (1.00")
Common Lumber Sizes — Board Feet Reference
Thickness Width Length Board Feet
Board Feet by Length (current thickness × width)
Log scaling rules estimate the usable board footage from a raw log. Different rules are used in different regions:
• Doyle — common in hardwood regions (eastern US), tends to underestimate small logs.
• Scribner — widely used in western US for softwoods.
• International ¼" — most accurate; used by USDA Forest Service.
Measured at the small end of the log, inside bark.
Please enter a valid diameter (≥ 1).
Standard log lengths: 8, 10, 12, 14, 16 ft.
Please enter a valid length (≥ 1).
Number of identical logs.
Enter price per board foot to calculate total cost.
Log Scaling Results
Doyle Rule
64.00 BF
Scribner Rule
79.00 BF
International ¼" Rule
92.89 BF
Rule Comparison — Board Feet by Diameter (at current length)
Log Board Feet Reference Table (16 ft log)
Diameter (in) Doyle (BF) Scribner (BF) Intl ¼" (BF)

Introduction

A board foot is a standard unit of measurement used in the lumber industry. It equals a piece of wood that is 1 inch thick, 12 inches wide, and 12 inches long.1 Knowing how to calculate board feet is important when you are buying or selling lumber for a construction project. This Board Foot Calculator makes it quick and easy to figure out exactly how much lumber you need. Just enter the thickness, width, and length of your boards, along with the number of pieces, and the tool calculates the total board feet. This helps you plan your materials, estimate costs, and avoid waste on your next building project.

How to use our Board Foot Calculator

Enter your lumber or log dimensions below, and this calculator will give you the total board feet and an optional cost estimate. The tool has two tabs: one for lumber boards and one for raw logs.

Lumber Board Feet Tab

Thickness: Type in the thickness of your board. You can use quarter notation like 4/4 or 8/4, a fraction like 1 1/2, or a decimal like 1.5. Then pick your unit (inches, feet, centimeters, or millimeters). The calculator rounds your thickness up to the nearest quarter inch.

Width: Enter the width of your board as a whole number, fraction, or decimal. Choose your unit from the dropdown menu next to the field.

Length: Enter the length of your board. The default unit is feet, but you can switch to inches, centimeters, or millimeters if needed.

Quantity (Number of Boards): Type in how many identical boards you have. The calculator will multiply the board feet per piece by this number to give you a total.

Price per Board Foot (optional): If you want to know the total cost, enter the dollar amount you pay per board foot. Leave this blank if you only need the board footage.

Log Board Feet Tab

Small-End Diameter (inside bark): Enter the diameter measured at the small end of the log, inside the bark. You can enter this in inches or centimeters.

Log Length: Enter the total length of the log in feet or meters. Common log lengths are 8, 10, 12, 14, and 16 feet.

Number of Logs: Enter how many identical logs you have. The calculator will show per-log results and totals for all logs when you have more than one.

Price per Board Foot (optional): Enter a dollar amount per board foot to see cost estimates. The calculator shows results using three standard log scaling rules (Doyle, Scribner, and International ¼ inch), so you can compare board foot estimates and costs across each method.

What Is a Board Foot?

A board foot is the standard unit used to measure lumber volume in the United States and Canada. One board foot equals a piece of wood that is 1 inch thick, 12 inches wide, and 12 inches long.1 That is 144 cubic inches of wood. Lumber yards, sawmills, and hardwood dealers all use board feet to price and sell wood. If you want to know how much wood you need for a project or how much it will cost, you need to understand board feet.

How to Calculate Board Feet for Lumber

The board foot formula for sawn lumber is simple:

Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12

For example, a board that is 1 inch thick, 6 inches wide, and 8 feet long equals 4 board feet. If you have 10 of those boards, you have 40 board feet total. The calculator above does this math for you instantly and also handles fractions, different units, and cost estimates.

What Is Quarter Thickness?

Hardwood lumber is often sold using a "quarter" system for thickness. In this system, 4/4 means the board is roughly 1 inch thick, 5/4 means about 1.25 inches, 6/4 means about 1.5 inches, and 8/4 means about 2 inches. Each "quarter" represents one-quarter of an inch. Lumber dealers round up to the nearest quarter when calculating board feet for pricing. This is called "quarterizing" the thickness, and the calculator above handles this automatically.

How to Calculate Board Feet from Logs

Estimating board feet from a raw log is different from measuring sawn lumber. Because a log is round and has bark, taper, and waste from sawing, you cannot get 100% of the wood turned into usable boards. Log scaling rules were created to estimate how many board feet of lumber a log will actually produce. Only three are widely recognized and in current use2:

  • Doyle Rule: This is the most widely used rule, especially on private timber in the eastern and southern United States.2 It uses the formula BF = (D − 4)² × L ÷ 16, where D is the small-end diameter inside the bark in inches and L is the length in feet.2 It badly underestimates small logs and overestimates large logs, and it ignores taper.2
  • Scribner Rule: This rule was widely used by the Forest Service in the Lake States and the western United States, where cubic measurement has recently replaced it.2 It was worked out by drawing 1-inch boards inside circles, so its values jump in steps.2 The calculator uses Bruce and Schumacher's smoothing formula, BF = (.79D² − 2D − 4) × L ÷ 16.2 On small logs it gives a closer estimate than Doyle.2
  • International ¼-Inch Rule: This is probably the most accurate of the three, though it is the least used.2 It allows for a ¼-inch saw kerf and a taper of ½ inch in diameter for every 4 feet of length.2 For each 4-foot section it uses BF = 0.199D² − 0.642D, and its values are rounded to the nearest 5 board feet.2

The measurements you need for log scaling are the small-end diameter (measured inside the bark at the narrow end of the log, in two directions at right angles, then averaged) and the log length.2 Standard log lengths are typically 8, 10, 12, 14, or 16 feet.

Why Board Feet Matter in Construction and Woodworking

Board feet are the basis for buying and budgeting rough lumber. Knowing your board footage helps you order the right amount of material and avoid overspending when framing a house, building furniture, or buying hardwood for flooring. Prices for species like oak, walnut, cherry, and maple are almost always listed per board foot. By multiplying your total board feet by the price per board foot, you get your total lumber cost.

Tips for Accurate Measurements

  • Always measure the actual thickness of rough lumber, not the nominal size. A "1-inch" board from a sawmill is truly 1 inch thick before planing.
  • For surfaced (S2S or S4S) lumber, you may still be charged based on the rough thickness before planing.
  • When measuring width on boards with irregular edges (live edge or waney edge), use the average width.
  • Add 10–20% extra to your total board footage to account for waste from cuts, defects, and unusable sections.

Formulas used

Lumber Board Feet 1
BF = \frac{T_q \times W \times L}{12}
Quarterized Thickness
T_q = \frac{\lceil T_{in} \times 4 \rceil}{4}
Doyle Log Rule 2
BF = \frac{(D - 4)^{2} \times L}{16}
Scribner Log Rule (Bruce and Schumacher formula) 2
BF = \frac{(.79\,D^{2} - 2D - 4) \times L}{16}
International ¼" Rule (per 4-ft section, total rounded to the nearest 5 BF) 2
BF_{4\,\text{ft}} = 0.199\,D_i^{2} - 0.642\,D_i, \quad D_{i+1} = D_i + \tfrac{1}{2}
Total Cost
C = BF_{total} \times P

Frequently asked questions

What is the board foot formula?

The board foot formula is: Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12. For example, a board that is 2 inches thick, 6 inches wide, and 10 feet long equals 10 board feet. This calculator also handles fractions and different units.

How many board feet are in a 2x4?

A standard 2×4 that is 8 feet long has 5.33 board feet. The math is: (2 × 4 × 8) ÷ 12 = 5.33 BF. Keep in mind this uses the nominal size (2 inches by 4 inches), not the actual dressed size of 1.5 by 3.5 inches. In the lumber trade, board feet for lumber 1 inch or thicker are figured on the nominal thickness and width and the actual length.1

How do I convert board feet to square feet?

To convert board feet to square feet, divide the board feet by the thickness of the lumber in inches. For example, if you have 100 board feet of 1-inch-thick lumber (4/4), that covers 100 square feet. If the lumber is 2 inches thick (8/4), 100 board feet covers only 50 square feet.

What does 4/4 mean in lumber thickness?

The number 4/4 means the board is four quarters of an inch thick, which equals 1 inch. This quarter system is standard for hardwood lumber. Here are common sizes:

  • 4/4 = 1 inch
  • 5/4 = 1.25 inches
  • 6/4 = 1.5 inches
  • 8/4 = 2 inches
  • 12/4 = 3 inches
  • 16/4 = 4 inches

What is the difference between Doyle, Scribner, and International log rules?

These are three methods used to estimate how many board feet of lumber you can cut from a raw log:

  • Doyle: The most widely used rule, especially on private timber in the east and south. It underestimates small logs badly and overestimates large ones.2
  • Scribner: Widely used by the Forest Service in the Lake States and the West. It is closer than Doyle on small logs, but its values jump in steps.2
  • International ¼": Probably the most accurate, because it allows for saw kerf and log taper, though it is the least used.2

The log tab in this calculator shows all three results so you can compare them.

How do I measure a log for board feet?

You need two measurements: the small-end diameter and the log length. Measure the diameter at the narrow end of the log, inside the bark, in two directions at right angles to each other, and average the two.2 Logs are seldom perfectly round. Then measure the total length of the log. Enter both numbers into the Log Board Feet tab to get your estimate.

How many board feet are in a 12-inch diameter log?

For a 12-inch diameter log that is 16 feet long, the published log rule tables give:

  • Doyle Rule: 64 board feet2
  • Scribner Rule: 79 board feet2
  • International ¼" Rule: 95 board feet2

The calculator's Scribner result uses the Bruce and Schumacher formula, which gives about 86 board feet for this log. The exact amount depends on which scaling rule is used in your area.

How much waste should I add to my board foot estimate?

You should add 10% to 20% extra to your total board footage. This covers waste from cuts, saw kerf, defects like knots or splits, and unusable sections. If the lumber has a lot of natural edge or is lower grade, plan for closer to 20% extra. For clean, select-grade boards, 10% is usually enough.

What is the difference between nominal and actual lumber size?

Nominal size is the name given to lumber, like 2×4 or 1×6. Actual size is the real measurement after the wood is dried and planed smooth. A nominal 2×4 actually measures 1½ × 3½ inches when dry.3 For rough-sawn hardwood, the nominal and actual sizes are usually the same. When calculating board feet for rough lumber, use the actual measured thickness.

How do I calculate the cost of lumber using board feet?

Multiply your total board feet by the price per board foot. For example, if you need 50 board feet of red oak priced at $6.50 per board foot, your cost is 50 × $6.50 = $325.00. You can enter a price in this calculator's optional price field, and it will calculate the total cost for you automatically.

How many board feet are in a cubic foot?

There are 12 board feet in one cubic foot. A board foot is 144 cubic inches (1" × 12" × 12"), and a cubic foot is 1,728 cubic inches. Dividing 1,728 by 144 gives you 12. So if you know the volume of wood in cubic feet, multiply by 12 to get board feet.

What types of wood are sold by the board foot?

Most hardwood lumber is sold by the board foot. This includes species like oak, walnut, cherry, maple, ash, poplar, and mahogany. Softwood dimensional lumber (like 2×4s and 2×6s) is usually sold by the linear foot or per piece, not by the board foot. Specialty softwoods from sawmills may also be sold by the board foot.

What is a board foot vs a linear foot?

A board foot measures volume: it accounts for the thickness, width, and length of the wood. A linear foot measures only the length, no matter how thick or wide the board is. Hardwood is sold by the board foot because boards come in random widths. Dimensional softwood is sold by the linear foot because the cross-section is standardized.

Sources

  1. Glossary (Wood Handbook: Wood as an Engineering Material, FPL-GTR-282). USDA Forest Service, Forest Products Laboratory. 2021;Board Foot. Accessed September 26, 2026.
  2. Cassens D. Log and Tree Scaling Techniques (FNR-191). Purdue University Cooperative Extension Service. pp. 1-3, Tables 1, 2A and 3. Accessed September 26, 2026.
  3. Senalik CA, Farber B. Commercial Lumber, Round Timbers, and Ties (Wood Handbook: Wood as an Engineering Material, FPL-GTR-282, Chapter 6). USDA Forest Service, Forest Products Laboratory. 2021;Table 6-6. Accessed September 26, 2026.

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