Rho measures how much an option's price changes for a one-percent change in interest rates. It is the fifth and least-discussed of the option greeks - real, but rarely the thing that decides a short-term trade.

Why rates affect options at all

Interest rates factor into option pricing because holding an option ties up (or frees up) capital versus holding the stock. Higher rates modestly increase call values and decrease put values, all else equal - the "cost of carry." For long-dated options, a big shift in rate expectations can move premiums noticeably.

Why intraday traders ignore it

Rho's impact scales with time to expiration. For the short-dated options most active traders use - days to a few weeks - rho is tiny compared to delta, theta, and vega. Rates don't move enough intraday to matter, and short options have little rho to begin with. It rounds to noise.

For a 1DTE options trade, rho is a rounding error. Spend your attention on delta, theta, and vega.

When to care

Rho matters for LEAPS and other long-dated positions, and in environments where rate expectations swing hard - around FOMC decisions, for instance, though even then the rate surprise moves stocks (delta) far more than it moves rho directly. For the short-term trader, know rho exists, then move on.