Prospective investors can think that SIPs and mutual funds are the same. However, SIPs are merely a method of investing in mutual funds, the other method being a lump sum. A SIP calculator is a tool that helps you determine the returns you can avail when parking your funds in such investment tools. Systematic Investment Plan or SIP is a process of investing a fixed sum of money in mutual funds at regular intervals. SIPs usually allow you to invest weekly, quarterly, or monthly.