Classic and classical look similar, but they are not interchangeable.
Classic usually means timeless, traditional, well known, or of high quality. It often describes something that has lasting value or is a standard example of its kind. For example, She prefers a classic navy blazer means the blazer has a simple, enduring style.
Classical usually relates to ancient Greece and Rome or to formal artistic traditions, especially music, literature, and art. For example, He studies classical mythology and piano uses the word for both the ancient world and the formal music tradition.
- Use classic for style, reputation, and lasting quality.
- Use classical for ancient civilizations and established art forms.
A quick contrast can help: a classic novel is a respected, lasting book, but classical literature usually points to literature from the ancient world or literature studied in a formal tradition.
If you mean timeless, choose classic. If you mean ancient or art related, choose classical.