How are the mutual fund SIP returns calculated after one year of investment?

You take the NAV of the starting date, and the latest NAV and then calculate the return.

Returns = 100 * (NAV2/NAV1 – 1)

If you invest in regular plans, then the returns will be about 1% or so lesser than Direct Plans. This is because the latter carry ZERO commission. Over time this difference compounds to a huge difference of about 40% or more.

Go with an advisor who offers only direct plans, not just for the zero commission but also because you get honest advice. No peddling of funds that carry higher commission.