Definition of Benchmark
A benchmark is a standard index against which a mutual fund's performance is measured and compared. Every SEBI-classified mutual fund must declare a benchmark. For example, large cap funds are typically benchmarked against the Nifty 50 or Nifty 100, mid cap funds against the Nifty Midcap 150, and multi cap funds against the Nifty 500.
Benchmarking helps investors judge whether the fund manager is adding value (alpha) through active stock selection, or whether the fund is simply performing in line with or below the broad market. Consistently underperforming the benchmark (especially after fees) is a sign to consider switching to a passive index fund.
Always compare a fund's returns against its declared benchmark — not the Sensex or Nifty 50 — because different fund categories have different appropriate benchmarks. A small cap fund beating the Nifty 50 but underperforming the Nifty Smallcap 250 is actually underperforming for its category.