4Gb/s =how many MB = Kb = byte and character?

To convert from Gb/s (gigabits per second) to different units:

1 Gb = 1000 Mb
1 Mb = 1000 Kb
1 Kb = 1024 bytes
1 byte = 8 bits
1 character can be equal to 1 byte (with some exceptions for special characters)

4 Gb/s = 4 * 1000 Mb/s = 4000 Mb/s
4000 Mb/s = 4000 * 1000 Kb/s = 4,000,000 Kb/s
4,000,000 Kb/s = 4,000,000 * 1024 bytes/s = 4,096,000,000 bytes/s
4,096,000,000 bytes/s = 4,096,000,000 / 8 characters/s (approx.)

Therefore, approximately:
4 Gb/s ≈ 4000 Mb/s ≈ 4,000,000 Kb/s ≈ 4,096,000,000 bytes/s ≈ 512,000,000 characters/s