How to Calculate
Percentage for Finance
GST, salary hikes, investment returns, EMI breakdowns, discounts, and inflation — the complete guide to percentage calculations every Indian needs for smarter financial decisions.
Why Percentage Calculations Matter in Personal Finance
Virtually every financial decision involves percentages — your savings rate, EMI-to-income ratio, investment return, tax rate, GST calculation, salary hike, discount on a purchase, and inflation impact are all expressed as percentages. Misunderstanding a percentage calculation can mean overpaying on a purchase, misreading an investment return, or underestimating a tax liability. This guide covers the most common financial percentage calculations with formulas and practical Indian examples.
Core Percentage Formulas
| Calculation | Formula | Example |
|---|---|---|
| Find percentage of a number | Result = (% / 100) x Number | 18% of Rs 50,000 = Rs 9,000 |
| Find what % one number is of another | % = (Part / Whole) x 100 | Rs 9,000 of Rs 50,000 = 18% |
| Increase a number by % | New Value = Number x (1 + %/100) | Rs 50,000 + 10% = Rs 55,000 |
| Decrease a number by % | New Value = Number x (1 – %/100) | Rs 50,000 – 20% = Rs 40,000 |
| Find original value after % increase | Original = New Value / (1 + %/100) | Rs 55,000 after 10% rise = Rs 50,000 |
| Find original value after % decrease | Original = New Value / (1 – %/100) | Rs 40,000 after 20% fall = Rs 50,000 |
| % change between two values | Change% = (New – Old) / Old x 100 | Rs 60,000 from Rs 50,000 = 20% rise |
GST Percentage Calculations
GST is India’s most pervasive percentage calculation. Two essential formulas:
Adding GST: If a product costs Rs 8,500 and GST is 12%: GST amount = Rs 8,500 x 12/100 = Rs 1,020. Total price = Rs 9,520.
Removing GST (reverse calculation): If a bill shows Rs 9,520 inclusive of 12% GST: Base price = Rs 9,520 / 1.12 = Rs 8,500. GST component = Rs 9,520 – Rs 8,500 = Rs 1,020.
The reverse calculation is used by businesses claiming Input Tax Credit — they need the base price to record the purchase value correctly in books and GST returns. Use the CalcWise GST Calculator for instant add/remove GST computation on any amount.
Salary and Income Percentage Calculations
Salary Hike Percentage
Hike % = (New Salary – Old Salary) / Old Salary x 100
Rs 85,000 from Rs 72,000: Hike = (13,000 / 72,000) x 100 = 18.06%
Savings Rate
Savings Rate % = Monthly Savings / Monthly Income x 100
Saving Rs 25,000 from Rs 80,000 income: Savings Rate = 31.25% — above the recommended 25-30% minimum.
Tax Rate on Income
Effective Tax Rate % = Total Tax Paid / Gross Income x 100
Paying Rs 1,80,000 tax on Rs 12,00,000 income: Effective rate = 15% — lower than the marginal slab rate of 20-30% because of deductions.
Investment Return Percentage Calculations
Absolute Return
Return % = (Current Value – Invested Amount) / Invested Amount x 100
Rs 1.5 lakh current value on Rs 1 lakh investment: Return = (50,000 / 1,00,000) x 100 = 50% absolute return.
CAGR (Compound Annual Growth Rate)
CAGR = [(Final Value / Initial Value)^(1/Years) – 1] x 100
Rs 1.5 lakh in 3 years from Rs 1 lakh: CAGR = [(1.5/1.0)^(1/3) – 1] x 100 = 14.47% per annum.
CAGR is the correct way to compare investments of different durations — a 50% absolute return in 3 years (CAGR 14.47%) is better than a 30% absolute return in 1.5 years (CAGR 18.5%)? No — the 18.5% CAGR investment is superior. Always compare using CAGR, not absolute return.
Dividend Yield
Dividend Yield % = Annual Dividend per Share / Current Share Price x 100
A stock paying Rs 12 annual dividend trading at Rs 240: Dividend yield = 5%.
Loan and EMI Percentage Calculations
EMI-to-Income Ratio
EMI-to-Income % = Total Monthly EMI / Monthly Net Income x 100
Rs 35,000 EMI on Rs 90,000 take-home: Ratio = 38.9% — within the safe 40% guideline.
Interest Component of EMI (Month 1)
Monthly Interest = Outstanding Principal x Annual Rate / 12 / 100
Rs 40 lakh home loan at 8.5%: Month 1 interest = Rs 40,00,000 x 8.5 / 12 / 100 = Rs 28,333 (on an EMI of approximately Rs 35,000, 81% goes to interest in month 1).
Loan-to-Value (LTV) Ratio
LTV % = Loan Amount / Property Value x 100
Rs 60 lakh loan on Rs 80 lakh property: LTV = 75% — within most banks’ maximum 80% LTV for home loans.
Discount Percentage Calculations
Discount Amount: Discount = Original Price x Discount% / 100
Final Price: Final = Original Price x (1 – Discount%/100)
Effective Discount % on stacked discounts: If a Rs 10,000 item has 20% off and then an additional 10% off: First discount = Rs 8,000; Second discount = Rs 7,200. Effective discount = (10,000 – 7,200) / 10,000 x 100 = 28% (not 30% — stacked discounts never add linearly).
Inflation Percentage Calculation
Inflation shows how much more expensive things become over time:
Inflation Rate % = (Current Price – Previous Price) / Previous Price x 100
Petrol at Rs 105 now vs Rs 90 a year ago: Inflation = (105-90)/90 x 100 = 16.7% for that specific item.
To find what Rs 1 lakh buys after N years of X% inflation: Future Value = Rs 1,00,000 / (1 + X/100)^N
At 6% inflation for 10 years: Rs 1,00,000 / (1.06)^10 = Rs 55,839 in real purchasing power — your money loses nearly half its value.
Percentage Calculation Quick Reference
- GST-inclusive price to base price: divide by (1 + GST rate as decimal). Rs 11,800 at 18% GST: 11,800 / 1.18 = Rs 10,000
- To increase by X%: multiply by (1 + X/100). 15% increase on Rs 40,000: 40,000 x 1.15 = Rs 46,000
- To find % change: (New – Old) / Old x 100. Both positive and negative results are expressed as percentages
- EMI-to-income should stay below 40% of net take-home
- Savings rate should be minimum 25% of gross income
- CAGR is always the correct metric for comparing investment returns across different time periods
- Use the CalcWise Percentage Calculator for any calculation not covered by the specific financial calculators
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Frequently Asked Questions
The basic percentage formula is: Percentage = (Part / Whole) x 100. For example, if you scored 450 marks out of 500, your percentage is (450 / 500) x 100 = 90%. In finance, this formula is applied universally: to calculate what percentage of your salary goes to EMI (EMI / Monthly Salary x 100), what percentage discount you received (Discount Amount / Original Price x 100), or what percentage of a goal amount you have saved (Saved Amount / Goal Amount x 100). To find a value after applying a percentage: Value = (Percentage / 100) x Base Amount.
To add GST to a price: GST Amount = Price x GST Rate / 100; Total with GST = Price + GST Amount. Example: Price Rs 10,000, GST 18%: GST = Rs 1,800; Total = Rs 11,800. To find the base price excluding GST from a GST-inclusive price: Base Price = GST-Inclusive Price / (1 + GST Rate/100). Example: Bill is Rs 11,800 inclusive of 18% GST: Base Price = Rs 11,800 / 1.18 = Rs 10,000. This reverse calculation is essential for claiming input tax credit correctly in GST returns.
Salary hike percentage = (New Salary – Old Salary) / Old Salary x 100. If your salary goes from Rs 50,000 to Rs 58,000: Hike percentage = (58,000 – 50,000) / 50,000 x 100 = 16%. To calculate the new salary after a known hike percentage: New Salary = Old Salary x (1 + Hike% / 100). For a 20% hike on Rs 50,000: New Salary = Rs 50,000 x 1.20 = Rs 60,000. To compare cumulative hikes over multiple years, use compound growth: Final Salary = Initial Salary x (1 + Annual Hike%)^Number of Years.
In the early months of a loan, most of the EMI is interest; later months shift towards principal repayment. For any EMI month: Interest Component = Outstanding Principal x Monthly Interest Rate (Annual Rate / 12 / 100). Principal Component = EMI – Interest Component. To express as percentages: Interest % of EMI = Interest Component / EMI x 100; Principal % = Principal Component / EMI x 100. For a home loan at 9% on Rs 50 lakh, month 1 EMI of Rs 44,986: Interest = Rs 50,00,000 x 0.75% = Rs 37,500 (83.4% of EMI); Principal = Rs 7,486 (16.6% of EMI). This ratio shifts gradually over the tenure as outstanding balance reduces.
Absolute return percentage = (Current Value – Cost) / Cost x 100. For Rs 1 lakh invested, now worth Rs 1.35 lakh: Return = (35,000 / 1,00,000) x 100 = 35% absolute return. For annualised return (CAGR): CAGR = (Final Value / Initial Value)^(1/Number of Years) – 1, multiplied by 100 for percentage. If Rs 1 lakh became Rs 1.35 lakh in 2.5 years: CAGR = (1.35/1.00)^(1/2.5) – 1 = 12.6% per annum. CAGR is the most meaningful return metric for comparing investments across different time periods.
The standard guideline is that total EMI obligations should not exceed 40-50% of monthly net take-home income. Calculation: EMI-to-Income Ratio (%) = Total Monthly EMI / Monthly Take-Home Salary x 100. If take-home is Rs 80,000 and total EMI (home loan + car loan + personal loan) is Rs 30,000: EMI-to-Income Ratio = 30,000 / 80,000 x 100 = 37.5% — within the 40% guideline. For home loans specifically, most banks cap the EMI at 40-50% of gross monthly income for eligibility. Keeping EMI below 35% leaves room for savings, emergency fund, and lifestyle expenses without financial stress.