Egg sizes are not as simple as recipes may indicate. The below gives some reference points. Of note, in the United States, the USDA guidelines give minimum weights. Therefore, average weights are often used and are provided here. In the UK, a range is given. The average sizes for Canada and the USA are less than a gram different for each size, so they are combined together below.
Of note, market eggs can vary greatly. Therefore, you might want to weigh some to get a feel for the size. BTW, these are weights in the shell.
Standard Egg Sizes Comparisons