In Korean
Click on the picture for the link to calculate the subway fare.
I'm afraid you must be able to read Hangul to use the calculator.
Check here on the how to do the calculation.
For Seoul Subway Calculator in English , click here.
Check here on the how to do the calculation.
For Seoul: http://www.seoulmetro.co.kr/station/eng/linemap.action?eng=Y
For Busan: http://www.humetro.busan.kr/english/03/01_01.php