About the income tax calculator
Since the new regime became the default in AY 2024-25, the question stopped being what your tax is and became which regime to be in. That is not a question you can answer from the slab rates alone, because the two systems differ in what they let you subtract before the rates apply — and for most people the deductions decide it, not the rates.
The new regime has wider bands and a much larger rebate: for AY 2026-27, nothing at all is payable up to twelve lakh of taxable income, which after the seventy-five thousand standard deduction means a salary of twelve lakh seventy-five thousand. What it takes away is nearly everything else — 80C, 80D, HRA, home loan interest, the lot. The old regime keeps all of them and taxes what remains at higher rates from a lower starting point.
So the comparison only means anything if the deductions are modelled properly, which is why every one of them is here rather than a simplified subset. One deserves special mention: 80CCD(2), the employer's contribution to your NPS, survives into the new regime. A comparison that quietly drops it understates the new regime for anyone whose employer offers it.
HRA is the deduction people most often get wrong. The exemption is the least of three figures — the allowance you received, the rent you paid minus ten percent of your salary, and half your salary in a metro or forty percent elsewhere. It is almost never the rent you paid, the salary in that formula is basic plus DA rather than gross, and 'metro' is a legal list of four cities rather than a judgement about how expensive somewhere is. The tool shows all three legs so you can see which one is binding.
Two thresholds behave strangely and are worth knowing about. The old regime's rebate stops dead at five lakh with no marginal relief, so one rupee of taxable income over the line costs about thirteen thousand. The new regime's rebate does have relief, so going slightly over twelve lakh costs only roughly what you went over by. Both are modelled here, along with surcharge and its own marginal relief above fifty lakh.
Slabs, caps and thresholds come from the Income Tax Department's published tables and are dated in the source. They change every Budget, so treat any figure here as indicative and check against your own Form 16 before filing.