Rho (ρ)

A metric used to determine how sensitive an option is to risk-free interest rate changes

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Written by CFI Team

What is Rho?

In finance, rho is a metric used to determine how sensitive an option is to risk-free interest rate changes. Arguably the least important and least used of the Greek option metrics, rho is typically expressed in a dollar amount. The metric shows how much money an option stands to gain or lose if the risk-free interest rate (in the US, the current interest rate paid on US Treasury bills) changes by 1%.

Rho

Summary:

Rho is a metric used for assessing the sensitivity of an option to changes in the risk-free interest rate.
Increasing interest rates typically favor call options, while interest rate decreases usually raise the value of put options.
However, interest rates typically have only a small influence on option pricing, which is more likely to be driven by variables such as volatility and dividend yield.

Understanding Positive and Negative Rho

Interest rate increases usually increase the value of long options – calls – and decrease the value of short options – puts. Therefore, long calls and short puts have a positive rho; long puts and short calls have a negative rho.

However, the truth is that rho is not a factor that ordinarily has a significant effect on option prices. Interest rates tend to only significantly shift option prices when there is a major and/or unexpected change in the risk-free rate. For example, if an announcement were made following a Federal Open Market Committee (FOMC) meeting that the Fed was decreasing the prime lending rate by half a percent – and the decrease in rates was very unexpected – then rho would likely have a significant impact on option prices. However, it would really just be in line with the overall market impact of such a sudden, unexpected rate change, which would most likely lead to notably increased market volatility, which, in turn, is typically reflected in higher option prices.

Interest rates and any interest rate changes commonly have more of an impact on options (which is reflected in the value of rho) as the option’s expiration date approaches. Additionally, Long-Term Equity Anticipation Securities (LEAPS) options, precisely because of their longer-term timeframe, are more sensitive to changes in interest rates than regular options, which have a significantly shorter lifespan.

Types of Options

Let’s examine the three primary option conditions in relation to rho:

1. Out-of-the-Money (OTM)

Out-of-the-money options are either put options with a strike price that is lower than the market price – or call options with a strike price above the current market price of the underlying stock. Out-of-the-money options have no intrinsic value but do have time value, as the market price may rise or fall sufficiently to put the option in-the-money prior to expiration. Rho shows a low value for options that are well out-of-the-money.

2. At-the-Money (ATM)

At-the-money options have a strike price that is the same as, or virtually the same as, the underlying asset’s current market price. Call and put options that are simultaneously at-the-money may both increase in value, especially if the underlying stock’s future price trend is widely perceived as uncertain. In such a case, rho may provide a clue as to whether the underlying stock’s future price trend is more likely to be bullish or bearish. Is the call option or put option exhibiting a higher rho and commanding a higher premium? The option that is receiving the most interest from investors is probably the one most likely to pay off.

3. In-the-Money (ITM)

In-the-money options have intrinsic value to the extent that their strike price is in-the-money: a call option with a strike price below the current market price or a put option with a strike price above the market price. They also have time value, as their strike price may become deeper in-the-money prior to the option’s expiration. Rho values are highest for options with a strike price that is either at-the-money or in-the-money.