CFT calculator
Pick the kind of timber, enter each size and add as many lines as you need. The rate is optional - fill it in to see the amount.
CFT = girth × girth × length × pieces ÷ 2304
| Girth (in) | Width (in) | Thickness (in) | Length (ft) | Pieces | CFT | Remove |
|---|
What CFT means
CFT is cubic feet - the volume of wood. One cubic foot is a block 1 ft × 1 ft × 1 ft, which is 12 × 12 × 12 = 1,728 cubic inches. Timber yards in Tamil Nadu buy and sell both logs and sawn timber by the CFT, so the rate you are quoted is usually a price per cubic foot.
CFT formula for sawn timber and planks
Width and thickness are measured in inches, length in feet:
CFT = width (in) × thickness (in) × length (ft) × pieces ÷ 144
Dividing by 144 (12 × 12) turns the two inch measurements into feet, so the answer comes out in cubic feet.
Example
Five pieces of 6″ × 4″, each 10 ft long:
6 × 4 × 10 × 5 ÷ 144 = 1,200 ÷ 144 = 8.33 CFT
CFT formula for round logs (quarter-girth method)
A log is measured by its girth - the distance around it - in inches, and its length in feet. The trade uses the quarter-girth rule (also called the Hoppus rule):
CFT = girth (in) × girth (in) × length (ft) ÷ 2304
The 2304 is 16 × 144: a quarter of the girth, squared, gives the cross-section of the square beam that can be sawn from the log. That is why this figure is lower than the log's true volume - about 78.5% of it. The rest is the rounded outside that is lost when the log is squared up.
Example
One log with a 48″ girth, 10 ft long:
48 × 48 × 10 ÷ 2304 = 23,040 ÷ 2304 = 10.00 CFT
For several logs of the same size, multiply by the number of logs.
CFT per foot of length - quick reference
| Girth (in) | CFT per foot of length | A 10 ft log |
|---|---|---|
| 24 | 0.25 | 2.50 CFT |
| 36 | 0.56 | 5.62 CFT |
| 48 | 1.00 | 10.00 CFT |
| 60 | 1.56 | 15.62 CFT |
| 72 | 2.25 | 22.50 CFT |
How to measure a log
- Girth: wrap a measuring tape around the log at the middle of its length and read it in inches.
- Only know the diameter? Girth = diameter × 3.14. A 15″ diameter is about a 47″ girth.
- Length: measure end to end in feet.
- Bark: ask whether the girth is taken over or under the bark - it changes the figure, so agree on it before you compare quotes.
Working in centimetres and metres
- 1 inch = 2.54 cm, and 1 foot = 30.48 cm (0.3048 m).
- 1 CFT = 0.0283 cubic metres, and 1 cubic metre = 35.31 CFT.
For example, a plank 15 cm × 10 cm × 3 m is 0.15 × 0.10 × 3 = 0.045 m³, which is 0.045 × 35.31 = 1.59 CFT.
From CFT to price
Amount = total CFT × rate per CFT
If the 8.33 CFT of planks above were quoted at ₹1,000 per CFT (an example, not our price), the amount would be 8.33 × 1,000 = ₹8,330, before tax and transport. Rates depend on the wood, the grade and the size of the pieces, and a quote may give separate rates for first and second quality. Ask us for today's rate.
Common mistakes
- Mixing units. Width and thickness in inches, length in feet. Entering length in inches makes the answer 12 times too big.
- Using diameter as girth. For logs the formula needs girth. Using the diameter gives an answer about ten times too small.
- Forgetting the pieces. Multiply by the number of identical pieces or logs.
- Rounding too early. Work out each line in full, then round. Our slips round each line down to two decimals, and the calculator above does the same.
Next steps
Need timber cut to these sizes? See our wood cutting and sizing service, or browse teak wood logs and all wood logs.