The Big Mac Index — a real-world ruler for currency value

What is the Big Mac Index?

The Big Mac Index is a shortcut for purchasing power parity (PPP) — the theory that, over time, exchange rates should move so that identical goods cost the same everywhere. Invented in 1986 as a light-hearted teaching tool, it has quietly become one of the most cited references in macroeconomic commentary.

The logic is simple: a Big Mac is a near-identical basket of labor, rent, beef, wheat, energy, and local taxes. If it costs $7.69 in the US and the equivalent of $4.23 in Portugal, the euro is cheap against the dollar in purchasing-power terms. If the market exchange rate agrees, the currency is “fairly valued.” If it doesn’t, one of them is — in theory — mispriced.

Today the index lives on at thebigmacindex.com, which refreshes daily via real Uber Eats menu scraping — a more current dataset than the twice-yearly editorial survey by The Economist.

The formula, in one line

That’s it. A currency is “overvalued” if its Big Mac costs more than the US one after converting at the spot rate, and “undervalued” if it costs less. A deviation of roughly ±10% is usually taken as the boundary between fair value and meaningful mispricing.

Three ways to read the number

A single currency produces three different index values depending on what you’re trying to compare. The methodology page goes deep on each; the short version:

Daily data vs. biannual survey

The Economist updates its Big Mac Index twice a year by calling local McDonald’s franchises. thebigmacindex.com takes a different approach: it scrapes real Uber Eats menus every day. The result is the same index, with far more resolution.

What the Big Mac can’t tell you

The index is a ruler, not a scalpel. It’s useful exactly because it’s simple, which also makes it wrong in specific ways:

• Not a basket.
  A Big Mac is one product. A real cost-of-living basket includes rent, healthcare, education, transport — many of which scale differently with currency strength.
• Tradable bias.
  Currencies of countries with rich tourism, big export sectors, or commodity revenues often look systematically 'overvalued.' That's a feature of the economy, not a pricing error.
• Cultural variation.
  Big Macs aren't equally popular everywhere. Pricing reflects local demand (India's Maharaja Mac uses chicken; Israel's kosher variant has its own costs). The Economist excludes some markets for this reason.
• Delivery premium.
  Uber Eats prices are typically higher than in-store, which affects absolute levels. The ratios between countries are still informative — which is what the index is really about.

Why Money2069 references the Big Mac Index

The Money2069 Manifesto argues that money should target stable spending power — not a state’s balance sheet. For that to be more than philosophy, you need a measurable target. What does it actually mean for a currency to “hold purchasing power”?

The Big Mac Index is a working answer. It’s not the answer — a real spending-power-stable currency would track a basket far richer than one sandwich — but it demonstrates the principle: you canmeasure real purchasing power across borders using a repeatable, falsifiable method, and you canhold currencies accountable to it.

Explore the data

The full live dataset lives at thebigmacindex.com. A few starting points: