It's impossible to answer this question. The amount of physical money changes all the time as notes are made and lost or wear out. Also exchange rates- how much the money is worth compared to other currencies- change everyday. Today £1 might be worth $2, but tomorrow it might be $1.801 or $2.40. To make it easier to compare value, there needs to be a universal currency, and for centauries it has been gold.
now you might ask: How much Gold is there in the world?
This can't be accurately answered either. But we can try to work it out. In one year, 50 million troy ounces (that's the measurement of gold) is produced, which is enough to make a cube 4.3 m (14 ft) along each side, weighing 1 ½ million kilograms (3 million lbs). That's just about large enough to the living room of an average house. Today that cube might be worth about US $13 Billion, but its value changes all the time. What we don't know is how much gold has been produced throughout history. A good guess would be a cube between 20 m and 25 m (62 ft and 82 ft) along each side- which means the total amount of gold ever discovered would fit into a tennis court.