Wandurance.com

A travel budget stretches differently depending on where you go and how you travel. Wandurance is built for anyone trying to answer the same underlying question — "how long can I actually afford to be here?" — before they commit to a flight.
Wandurance starts from four baseline daily costs for a US traveler — accommodation, food, local transportation, and a small basic-medical-care buffer — for each lifestyle tier. Each destination then gets a relative price-level index (roughly: how expensive everyday goods and services are there compared to the US dollar), so a night's stay, a day of meals, a bus fare, and a clinic-visit reserve are all scaled to that country's local purchasing power before being converted back into a US-dollar figure.
That's the same idea behind purchasing-power-parity comparisons: rather than a live currency exchange rate, it reflects roughly how far a dollar actually stretches on the ground.