Cord of Wood Converter
Free Cord wood tool for home economics. Enter your details to get instant, tailored results and guidance. Includes formulas and worked examples.
Calculator
Adjust values & calculateEnergy Equivalents
Formula
A full cord equals 128 cubic feet (4 ft x 4 ft x 8 ft). Multiply your stack dimensions in feet to get cubic feet, then divide by 128 to get the number of cords. A face cord is typically 1/3 of a full cord with 16-inch log lengths.
Last reviewed: December 2025
Worked Examples
Example 1: Standard Cord Verification
Example 2: Face Cord Price Comparison
Background & Theory
The Cord of Wood Converter applies the following established principles and formulas. Unit conversion is the process of expressing a quantity in a different unit of measurement while preserving its physical meaning. At the foundation of modern measurement lies the International System of Units (SI), which defines seven base units: the meter for length, kilogram for mass, second for time, ampere for electric current, kelvin for thermodynamic temperature, mole for amount of substance, and candela for luminous intensity. All other units, called derived units, are defined as algebraic combinations of these seven. Dimensional analysis is the principal method for performing unit conversions. By treating units as algebraic quantities that can be multiplied, divided, and cancelled, a conversion factor chain allows a value expressed in one unit to be rewritten in another without altering its physical magnitude. For example, to convert 60 miles per hour to meters per second, one multiplies by a chain of conversion factors each equal to one: (1609.34 m / 1 mile) × (1 hour / 3600 s). Metric prefixes enable compact expression of quantities across extreme ranges of magnitude. Standard prefixes span from nano (10^-9) through micro (10^-6) and milli (10^-3) up through kilo (10^3), mega (10^6), and giga (10^9), and beyond in both directions. These prefixes are strictly multiplicative and apply consistently to any SI base or derived unit. Temperature conversions require affine transformations rather than simple scaling. To convert Celsius to Fahrenheit the formula is °F = (°C × 9/5) + 32, while the conversion to the absolute Kelvin scale is K = °C + 273.15. These formulas reflect the different zero points and degree-size conventions of each scale. Significant figures govern how precision is preserved through calculations. A result should not express more precision than the least precise input value permits. In digital storage, IEEE and IEC standards distinguish between decimal prefixes (kilobyte = 1000 bytes) and binary prefixes (kibibyte = 1024 bytes), a distinction that has practical consequences for how storage capacity is reported by manufacturers versus operating systems. Unit coherence — ensuring that all quantities in an equation share a consistent unit system — is essential for obtaining correct results.
History
The history behind the Cord of Wood Converter traces back through the following developments. Human beings have been measuring and comparing quantities since before recorded history. The earliest known measurement units were body-based: the cubit (the distance from elbow to fingertip), the foot, the hand, and the digit. The furlong originated as the length of a furrow a team of oxen could plow without resting. These anthropomorphic standards were practical for local use but differed between regions and kingdoms, creating persistent difficulties in trade and construction. The ancient Egyptians standardized the royal cubit at approximately 52.4 centimeters and distributed calibrated granite rods to ensure consistency across building projects, including the pyramids. Roman engineers used the mile (mille passuum, one thousand double paces) and spread these standards throughout their empire via road networks. Despite these efforts, measurement diversity persisted across medieval Europe, hampering commerce. The French Revolution created political will for radical standardization. In 1795 France officially adopted the metric system, defining the meter as one ten-millionth of the distance from the equator to the North Pole along the Paris meridian. This gave the world its first fully decimal, rationally constructed measurement system. The Metre Convention of 1875 established the International Bureau of Weights and Measures (BIPM) in Sevres, France, creating a permanent international body to maintain physical artifact standards and coordinate global metrology. For over a century, the kilogram was defined by a platinum-iridium cylinder locked in a vault near Paris. In 1999, a stark demonstration of what unit inconsistency costs occurred when NASA's Mars Climate Orbiter was lost because one engineering team used pound-force seconds while another used newton seconds. The spacecraft entered the Martian atmosphere at the wrong angle and was destroyed, at a cost of 327 million dollars. In 2019 the SI underwent its most significant revision, redefining all seven base units in terms of fixed numerical values of fundamental physical constants such as the speed of light, Planck's constant, and the elementary charge. This eliminated any reliance on physical artifacts and made the measurement system permanently stable and universally reproducible.
Frequently Asked Questions
Formula
Cords = (Length x Height x Depth) / 128
A full cord equals 128 cubic feet (4 ft x 4 ft x 8 ft). Multiply your stack dimensions in feet to get cubic feet, then divide by 128 to get the number of cords. A face cord is typically 1/3 of a full cord with 16-inch log lengths.
Worked Examples
Example 1: Standard Cord Verification
Problem: A firewood seller offers a stack of oak that is 8 feet long, 4 feet high, and 4 feet deep for $300. Is this a full cord and what is the energy value?
Solution: Volume: 8 x 4 x 4 = 128 cubic feet\nFull cord = 128 cubic feet, so this is exactly 1.000 cord\nOak BTU output: 1.0 x 24,000,000 = 24,000,000 BTUs (24.0 million)\nOil equivalent: 24,000,000 / 138,500 = 173.3 gallons\nGas equivalent: 24,000,000 / 100,000 = 240.0 therms\nCost per million BTU: $300 / 24 = $12.50
Result: Full Cord: Yes (128 cu ft) | 24.0M BTUs | Equals 173 gal oil or 240 therms gas
Example 2: Face Cord Price Comparison
Problem: A seller offers a face cord (8 ft long, 4 ft high, 16 inch logs) of maple for $150. What is the equivalent full-cord price?
Solution: Volume: 8 x 4 x 1.333 = 42.67 cubic feet\nCords: 42.67 / 128 = 0.333 cords (one-third)\nEquivalent full cord price: $150 / 0.333 = $450 per full cord\nThis is significantly more expensive than buying a full cord at typical $250-350 prices
Result: Face Cord = 0.333 full cords | Equivalent: $450/cord | Overpriced vs. $300 full cord
Frequently Asked Questions
What exactly is a cord of wood?
A cord of wood is a standard unit of measurement for firewood defined as a neatly stacked pile measuring 4 feet wide, 4 feet high, and 8 feet long, totaling 128 cubic feet. However, because logs are irregular and cannot pack perfectly, the actual solid wood content is approximately 80 to 90 cubic feet with the remainder being air space between logs. The cord measurement assumes wood is stacked tightly and uniformly without excessive gaps. This standard has been legally defined in most U.S. states and Canadian provinces to protect consumers from being shorted on firewood purchases. A cord is approximately 2 to 3 pickup truck loads depending on the truck bed size.
What is a face cord and how does it differ from a full cord?
A face cord, also called a rick or stove cord, is a stack of wood that is 4 feet high and 8 feet long but only as deep as the cut length of the logs, typically 16 inches instead of the full 4 feet deep of a standard cord. This means a face cord of 16-inch logs is one-third of a full cord, containing roughly 42.67 cubic feet versus 128 cubic feet. The term face cord is not a legally standardized measurement and can be misleading. Some sellers use it to charge disproportionately high prices compared to a full cord. Always ask for the dimensions and calculate the cubic footage to ensure you are getting a fair price per volume of wood.
How many BTUs does a cord of wood produce?
BTU output per cord varies by species and is directly related to wood density. Hickory produces the most heat at approximately 26.5 million BTUs per cord, making it the premium firewood choice. Oak (both red and white) produces about 24 million BTUs per cord and is the most popular firewood in the eastern United States. Hard maple produces about 24 million BTUs per cord as well. Birch generates roughly 20.8 million BTUs. Pine produces only about 17.1 million BTUs per cord but ignites easily, making it good for kindling. For comparison, one cord of oak provides roughly the same heat as 173 gallons of heating oil or 240 therms of natural gas.
How much does a cord of wood cost?
Cord prices vary significantly by region, season, wood species, and whether the wood is delivered and stacked. National average prices typically range from $150 to $400 per cord for mixed hardwoods. In the Northeast and Pacific Northwest, premium hardwoods like oak and maple can cost $300 to $500 per cord delivered. In the Southeast and rural Midwest, prices are often lower at $150 to $250 per cord. Prices are generally lowest in spring and summer when demand is low and highest in late fall and winter. Buying green wood and seasoning it yourself saves 20% to 40% compared to buying seasoned wood. Always price wood by the full cord rather than by face cord or truckload to make accurate comparisons.
How many cords of wood do I need for a winter?
Average consumption depends on your heating needs, climate, home insulation, and how you use your fireplace or stove. A home primarily heated with a high-efficiency wood stove in a cold northern climate typically burns 4 to 6 cords per season. An energy-efficient home using a wood stove as supplemental heat might use 2 to 3 cords per winter. Using a standard open fireplace for ambiance a few evenings per week might consume only 1 to 2 cords per season. Open fireplaces are about 10% to 15% efficient while modern wood stoves achieve 70% to 80% efficiency, meaning you need far less wood with a stove. Calculate your needs based on past usage or estimate based on your heating zone and equipment efficiency.
How do I compare wood heating costs to oil and gas?
To compare costs, calculate the cost per million BTUs for each fuel type. For wood, divide the price per cord by the BTU output in millions. For example, oak at $300 per cord produces 24 million BTUs, so the cost is $300 / 24 = $12.50 per million BTUs. For heating oil at $3.50 per gallon (138,500 BTUs per gallon), the cost is $3.50 / 0.1385 = $25.27 per million BTUs. For natural gas at $1.50 per therm (100,000 BTUs per therm), the cost is $1.50 / 0.1 = $15.00 per million BTUs. Adjust these calculations by your equipment efficiency, as a 75% efficient wood stove effectively costs $12.50 / 0.75 = $16.67 per million BTUs of actual delivered heat.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy