Torn calf muscle, when should I seek medical advice?

Immediately. If you have truly torn the muscle in your calf, you should see your doctor right away. The longer you wait, the more difficult repairing the torn muscle will be.
Now. You are at greater risk for venous thrombosis. You should seek medical assistance immediately and possibly have testing and an ultrasound done. It may be a more dangerous condition than a "torn calf muscle".

Related Questions

What can I do to heal a torn calf muscle quickly?

No easy answer. This will take time since this will need to heal on its own. In the beginning the principle of rice (rest, ice, compression, elevation) are mandatory. Make sure that you keep range of motion in your ankle and knee. Over stretching the calf will just continue to reinjure the muscle. Read more...