225/45 R16 doesn't belong to the most popular dimensions for tyres - there are tyre models available, which can be compared to 325/30 R21, 155/60 R15, 155/65 R13. Let's break down the sizing - 45 is height of the tyre, which is calculated as 45% of the tyre width (225mm), which means the sidewall height has 101.25 mm. The wheel diameter is R16, which means it fits to a 16 inch/406.4mm diameter wheel. The total circumference of the tyre is mm, which is very similar to 175/60 R14(1776.88 mm), 245/70 R17(2434.11 mm), 175/80 R14(1996.8 mm), 255/40 R18(2077.22 mm), 185/60 R14(1814.58 mm), 255/50 R19(2317.24 mm), 185/80 R14(2047.06 mm).