The best way to estimate your credit purchase requirements is to look at your current SMS subscriber list and how often you need to message them. For instance, let’s say you have 1200 contacts and want to message them all once a week (up to 160 characters), then the total credits required in a month will amount to around 4800 to 5000. You can do the math accordingly and purchase more credits as and when required with the flexibility of the pay-as-you-go pricing model.