Is there one single formula which allows to calculate the income of a person in PPP\$ from her income in LCUs (local currency units), given for example the PPP conversion factor, GDP (LCU per international $) as published by the World Bank.
Assume for example an Indian farmer with a monthly income of ₹50,000, given India's PPP conversion factor of 18 and exchange rate ₹70 = $1. What is his monthly income in PPP\$ and by which formula? Is other or further information needed?
Vice versa: What is the farmer's monthly income in rupees when his income is known to be PPP\$30?
GapMinder's Dollar Street
The Economic Lives of the Poor by Abhijit V. Banerjee and Esther Duflo