How to unlock phone by calculating the code?

Locked phones are wasted investments

• If you change to a new service provider, your old locked phone is useless and you must buy a completely new phone.
  
• When you travel abroad, a locked phone cannot be used with local prepaid SIM card.
  
• Locked phone cannot be sold.

There are a number of freewares for calculating the code, however they often have a less-polished UI and require you to know more about jargons. It can be frustrating to calculate the code. You may find the list of unlock code calculator programs here. You might need to try a number of unlock programs because they run in different Windows versions.

You might also try NokiaFREE with its online calculator at http://unlock.nokiafree.org/, which does the same thing as the offline software.

Older Nokia models usually use the old DCT3 firmware, while, most of today's Series 40 and Series 60 phones utilize the DCT4 firmware, which is luckily supported by most calculator programs. Examine the list of DCT3 phones at http://www.unlockme.co.uk/softwareversions.html. If your phone is not listed in this table, perhaps it is a DCT4 phone.

http://homepage.ntlworld.com/danluik/downloads/dct4nck.zip, is one of the simplest code calculator.

When it runs in DOS shell, it would display

DCT4NCK by jozso v0.0a

Usage: dct4nck locktype imei provider [boxserial]

In older phone locktype usually 2, but if you are using 3650 and 7650 above it is usually 5, also put your IMEI number and the provider code. You can get the provider code here.

This calculator would generate seven possible codes, however you only have 5 tries before the phone is locked,

Typically, you want to try the fourth one first, then the first one, and then the seventh one.

Locking mechanism is increasingly complex, this method will not probably work on newest phones.