Feet to metres
A foot (ft) is exactly 0.3048 m. At sea you meet it more often than the metric system suggests: draft marks on older ships, soundings on American charts, heights in aviation and in a lot of technical documentation. Type a value and the converter shows metres, inches, yards and fathoms at once.
Quick try:
The cable here is the international one, 0.1 NM (185.2 m); the US Navy counted 219.5 m and the Royal Navy 185.3 m. A shackle of anchor chain is 15 fathoms (27.43 m).
Feet converted to metres
| ft | m | yd | in |
|---|---|---|---|
| 1 | 0.3048 | 0.3333333 | 12 |
| 2 | 0.6096 | 0.6666667 | 24 |
| 3 | 0.9144 | 1 | 36 |
| 5 | 1.524 | 1.666667 | 60 |
| 6 | 1.8288 | 2 | 72 |
| 10 | 3.048 | 3.333333 | 120 |
| 20 | 6.096 | 6.666667 | 240 |
| 33 | 10.0584 | 11 | 396 |
| 50 | 15.24 | 16.66667 | 600 |
| 100 | 30.48 | 33.33333 | 1,200 |
Values computed from the exact definitions of the units (NIST SP 811 and the international agreements), rounded to 7 significant digits. The first column is feet.
Foot, yard, inch: how they fit together
The system is simple: 1 foot is 12 inches, 3 feet make a yard, 6 feet make a fathom. Since 1959 all of them have exact metric definitions (an inch is 25.4 mm), so nothing in these conversions is approximate.
One handy figure for the deck: 33 feet of seawater is roughly 10 metres, and 10 metres of seawater is roughly one atmosphere of pressure. That is why a diver at 10 m carries twice the pressure of the surface, and a sounding in feet divided by three gives you metres for a first look, about a tenth on the high side.
Frequent questions
How many centimetres is 1 foot?
Exactly 30.48 cm. Six feet are 1.8288 m, which is exactly one fathom.
How many feet are in a metre?
About 3.281 feet (exactly 1 divided by 0.3048). Ten metres are 32.81 feet.
Why are drafts sometimes given in feet?
Older ships and English-language documentation used feet, and draft marks in feet are 6 inches tall with a 6 inch gap. Modern marks are metric, but both systems are still in circulation, so read the marks before you read the number.
Are soundings on a chart in feet or in metres?
It depends on the chart. Modern charts are metric, but American charts often carry feet or fathoms. The unit is printed in the chart title and near the depth legend, and mixing them up is a classic grounding.