1 stone = 14lbs. Learned this "whilst" (another chiefly British word) at study abroad in England. Ever after thought of the Bush album "Sixteen Stone" in a different light.
Of course I never remember that a how much a pound is.
From my d&d days (when we mix and matched Italian and English material) I remember that 2.5lbs is about 1kg, but that's a very rough approximation. Similarly I remember that 10ft is ~3m.
