A SIP and a lump sum describe when money is invested. They do not identify the asset, guarantee a result or create a reliable winner.
SIP
A Systematic Investment Plan invests an amount at regular intervals. Each instalment purchases units at the applicable NAV. The number of units therefore varies through time, and every instalment has a different holding period.
Lump sum
A lump sum invests one amount at one point in time. The full amount is exposed to the subsequent return path from that date.
Why results differ
The outcome depends on the sequence of market returns, each payment date, the investment horizon, costs, taxes and the performance of the selected asset.
In one path a lump sum may finish higher; in another path periodic purchases may. SIP does not guarantee a lower average cost or better result in volatile markets, and “invest when the market is low” is not an implementable rule without knowing the future.
For a fair illustration, compare the same total contribution, asset assumptions and end date. Treat every entered return as a sensitivity input, not a forecast. The SIP Calculator and Lump Sum Calculator model their respective cash-flow timing conventions.