The seed of a carrot weighs about 1/1000th of a gm. An average carrot weighs about 100gm. So that means a carrot weighs 100,000 times more than the seed. The UK annual production of carrots is 700,000 tonnes over 9000 Hectares of land. If the farmers could turn every seed into a carrot then they would need 7 tonnes of carrot seeds. One hectare of land produces 78 tonnes of carrots and an allotment sized bit of land 1/40th of a hectare produces approx 2 tonnes of carrots. So allotmenteers if you intend to grow just carrots you will need 20 gms or 20,000 seeds - should be no more than about £10. Economy allotment growing.