Commonly used quantities in SI units

Here are some commonly used quantities in SI units:

• The diameter of a CD or DVD is 12 cm. The diameter of the centre hole is 15 mm.
• A typical doorknob is about 1 m high.
• The length of an unused pencil is 18 cm.
• The size of an A4 paper is 210 mm × 297 mm.
• The size of a single playing card is 88 mm × 63 mm.
• The size of a credit/debit card, an ID card, a driver's license,  a name card, etc. is 85.60 mm × 53.98 mm.
• The length of equator is about 40000 km.
• The length of a football pitch is about 90~120 m, and the width is about 45~90 m.
• The size of a basketball court is 28 m × 15 m.
• The length of the running track is 400 m. Each lane of the track is as wide as 122 cm.
• The sound speed in the air is about 340 m/s, and the light speed in vacuum is 299792458 m/s.
• The common speed of a car is 10~30 m/s  (40~120 km/h).
• The mass of 1 L water is 1 kg.
• The standard atmosphere pressure is 101325 Pa.
• The STP is defined as 273.15 K and 100 kPa.
• Water freezes at 273.15 K (0 °C) and boils at 373.15 K (100 °C) in 101325 Pa.
• Normal body temperature of human is about 310.15 K (37 °C). 310.65 K (37.5 °C) or above is fever.
• You will feel comfortable if the temperature is about 293.15 K (20 °C), hot when above 303.15 K (30°C) and cold when below 283.15 K (10 °C).
• The voltage of a dry cell is 1.5 V; and storage battery, 2.05 V. For the Li-ion battery, it is 3.7 V.
• For most countries/regions the voltage level is 220 V, and the frequency is 50 Hz.
• The safety voltage limit is about  36 V.