Big Mac PPP

What Does Big Mac PPP Mean?
A survey done by The Economist that determines what a country's exchange rate would have to be for a Big Mac in that country to cost the same as it does in the United States. Purchase power parity (PPP) is the theory that currencies adjust according to changes in their purchasing power. With the Big Mac PPP, purchasing power is reflected by the price of a McDonald's Big Mac in a particular country. The measure gives an impression of how overvalued or undervalued a currency is.

Investopedia explains Big Mac PPP
The calculation of the Big Mac PPP-adjusted exchange rate looks at the price of a Big Mac in a given country and divides it by the price of a U.S. Big Mac. Let's say that we are looking at the Big Mac in China. If a Chinese Big Mac is 10.41 renminbi (RMB) and the U.S. price is $2.90, then - according to PPP - the exchange rate should be 3.59 RMB for US$1. However, if the RMB was actually trading in the currency market at 8.27 RMB for US$1, the Big Mac PPP would suggest that the rmb is undervalued.