Two complementary calculations run in parallel. The aggressive cap is Income × Cap% - the upper bound most planners would recommend. The conservative figure is (Income × 25%) − Existing EMIs, accounting for the fact that EMIs are non-negotiable monthly outflows that compete with rent for the same fixed-cost share of income. Together they give you a safe range; staying near the conservative number gives maximum financial flexibility, near the cap means you're optimising for housing quality at the cost of other priorities.
Rent affordability should also factor HRA (House Rent Allowance) tax exemption. Salaried Indians paying rent can claim the lower of: actual HRA received, rent paid minus 10% of basic salary, or 50% of basic for metro cities (40% for non-metros). On a ₹50,000/month rent with ₹40,000 HRA component for someone in the 30% tax slab, the exemption saves roughly ₹10,000/month in tax - effectively reducing the real cost of rent by 20%. Use the HRA exemption calculator alongside this one for the post-tax view.
Beyond the rent itself, true housing cost includes maintenance and society charges (typically ₹2,000-8,000/month in apartments), parking (₹500-3,000), electricity and water (₹2,000-5,000), brokerage amortised over the lease period, and security deposit opportunity cost. Add 15-25% to the headline rent for a realistic total monthly housing cost when comparing offers.