A ruler that is one foot long is about as long as thirty cm. 30 cm are equal to 0.984251968504 feet since one centimetre is equal to 0.0328083989501 feet. You can round the converted length up to 1 foot.
The SI’s most used unit of measurement is the centimetre. Ten millimetres, or one hundredth of a metre, make up one centimetre. 30 centimetres are equal to 11.811023622 inches, or 12 inches if you round to the next full number, since one centimetre is equal to 0.393700787402 inches in inches. One foot is equivalent to twelve inches. The standard school ruler has 30 centimetres drawn on one side and 12 inches drawn on the other.