The imperial pint is the pint of the British imperial system. It is one eighth of the imperial gallon, which NIST lists as exactly 4.54609 L, and it holds 20 imperial fluid ounces. It is larger than the US liquid pint, which holds 16 US fluid ounces.
Conversion
imperial pt = imperial gal ÷ 8
mL = imperial pt × 568.26
imperial fl oz = imperial pt × 20
US pt ≈ imperial pt × 1.2009
Example
One imperial pint is 4.54609 ÷ 8 = 0.5682625 L, or 568.26 mL. Twenty imperial fluid ounces of 28.41306 mL give the same 568.26 mL. A US pint is 473.18 mL, so the imperial pint is 568.26 ÷ 473.18 = 1.20 times as large, a difference of about 95 mL.
Common mistakes
Treating the two pints as equal shifts a recipe by about 20%. Recipes written in imperial pints should be converted through millilitres. See how many cups in a pint for the US and UK comparison.