In most American English words, the /r/ is pronounced in all positions. In standard British English, unless you live in northern England, the /r/ is only pronounced before a vowel sound. Below are some examples.
Example 1: CAR
UK:
US:
Is the following British or American? (answer below)
1.
Example 2: OFFER
UK:
US:
Is the following British or American? (answer below)
2.
Example 3: GUITAR
UK:
US:
Is the following British or American? (answer below)
3.
Example 4: TURN
UK:
US:
Is the following British or American? (answer below)
4.
Example 5: FAR
UK:
US:
Is the following British or American? (answer below)