What is this calculator?
This calculator applies a progressive slab structure to a taxable income: each slab taxes only the portion of income that falls inside it. It carries no country's rates — you supply the slabs, which is what lets it stay correct across jurisdictions and years.
Use it when:
- You want to see how much tax each band of your income contributes.
- You are comparing two slab structures, such as an old and a new regime.
- You want the effective rate rather than the headline marginal rate.
Intended for: Taxpayers estimating a liability from published slab rates, and anyone learning how progressive taxation works.
How is this calculated?
- Each slab you supply defines a lower bound, an upper bound (or none, for the top slab), and a rate.
- For each slab, the calculator finds how much of your income falls within that band — never the whole income, only the portion above the slab's floor and below its ceiling.
- That portion is multiplied by the slab's rate to give the tax contributed by that band.
- Summing every band gives the total tax. This is why moving into a higher bracket never reduces your take-home pay: only the income above the threshold is taxed at the higher rate.
- The effective rate is the total tax divided by the whole taxable income — always lower than the top marginal rate you reached.
Formulas
Tax within one slab
Slab tax = max(0, min(Income, Max) − Min) × Rate / 100
Only the portion of income lying inside the band is taxed at that band's rate.
- Min
- Lower bound of the slab
- Max
- Upper bound of the slab (unbounded for the top slab)
- Rate
- Percentage rate applied within the slab
Effective rate
Effective % = Total tax / Taxable income × 100
The average rate across all your income — lower than the marginal rate of your highest slab.
Example
A taxable income of 100,000 against slabs of 0% up to 50,000, 10% from 50,000 to 80,000, and 20% above 80,000.
- First 50,000 at 0% → 0.
- Next 30,000 (50,000 to 80,000) at 10% → 3,000.
- Remaining 20,000 (above 80,000) at 20% → 4,000.
Result: Total tax 7,000, after-tax income 93,000, effective rate 7% — well below the 20% top marginal rate.
Frequently asked questions
Why is my effective rate so much lower than my tax bracket?
Because only the income above each threshold is taxed at that band's rate. Your bracket is the rate on your last unit of income; your effective rate averages across all of it.
Can earning more push me into a bracket that leaves me worse off?
Not under a purely progressive slab structure like this one. Only the additional income is taxed at the higher rate, so more gross income always means more net income.
Why do I have to enter the slabs?
Slab rates change with jurisdiction, regime, assessment year, and taxpayer category. Supplying them keeps the calculation accurate and transparent instead of silently using rates that may be out of date.
Does this apply deductions, exemptions, rebates, or surcharges?
No. It taxes the taxable income you supply. Deductions and exemptions must be subtracted before entering the figure, and rebates, surcharges, and cess must be applied afterwards.
Assumptions
What this calculator takes as given:
- The income entered is already the TAXABLE income, after all deductions and exemptions.
- The slabs supplied are contiguous, ordered, and complete for the jurisdiction.
- Tax within each band is a flat percentage of the portion of income inside it.
Limitations
What this calculator cannot know or does not model:
- It holds no country's rates and cannot tell you which slab structure applies to you.
- Rebates, surcharges, cess, alternative minimum taxes, and capital-gains rates are not modelled.
- Relief provisions, carried-forward losses, and set-offs are outside its scope.
- The result is an estimate for planning; a filed return should be prepared against the statute or with a qualified adviser.
References
- Progressive taxation and marginal versus effective rates — OECD Tax Policy Studies. General background on the slab mechanism; consult your own tax authority for the rates that apply to you.