The plural of calf is calves.
1. A calf is the young of a bovine mammal such as a cow. The word is also used to refer to the young of deer, elephants and whales.
2. The lower muscular area at the back of the leg below the knee.
The plural of calf is formed by replacing the letter f with the ending -ves to make the word calves.
This follows the same plural rule of many similar words such as half, shelf and wolf.
It is worth noting that the Merriam Webster dictionary states that the word calfs is also a plural form of the word calf.
The word calfs is not found in any of the other well known dictionaries and so we do not advise using this form of the word.
Indeed the graph below shows the usage of the words calves vs. calfs in written English since 1900. As you can see, the use of the word calfs in written English is so little as to be almost nonexistent.
Singular Example: A baby calf is born without an immune system. They need colostrum from their mothers as soon as they are born.
Plural Example: The calves were able to eat grass from as young as 2 weeks old.
The graph shows the occurances of the plural of calf in written English since 1800 using Google's Ngram Viewer.
Unlike humans, newborn calves are able to stand and walk immediately. Some people find this udderly amazing!