A part can be any type of measurement (e.g., cup, ounce, quart, etc.) but will always be equal. To calculate 1 part sugar and 4 parts water for your recipe, first choose a measurement for “one part.” Then, do some simple math:
1 x (chosen “one part” measurement) = total sugar
4 x (chosen “one part” measurement) = total water
For example, if you want to make a large batch of sugar water, you might decide that for your recipe 1 part = 2 cups.
1 x 2 cups = 2 cups sugar
4 x 2 cups = 8 cups water
So, in this example, you would mix 2 cups of sugar (1 part) with 8 cups of water (4 parts).
To make a smaller batch of sugar water, you might decide that for your recipe 1 part = ½ cup.
1 x ½ cup = ½ cup sugar
4 x ½ cup = 2 cups water
So, in this example, you would mix ½ cup of sugar (1 part) with 2 cups of water (4 parts).