Quick answer: Budget travelers can manage on $25–40/day, mid-range $70–120/day. India is very cash-based — carry rupees, and use ATMs in cities.
India offers some of the lowest daily costs anywhere, and cash rules outside the cities.
Daily budget
Budget: $25–40/day; mid-range: $70–120/day; luxury: $250+. A week (excluding flights) is roughly $175–840.
Cash vs card
Cards and UPI apps work in cities and chains; rural areas, rickshaws and markets are cash. ATMs are widespread in towns but can be sparse in remote areas.
How much cash to bring
Carry rupees for daily spending and keep small notes for tips and rickshaws. Withdraw enough before heading rural.
Tips
Notify your bank, keep a backup card, and carry a money belt for long journeys.