Last updated: June 2026
Our approach
CalcToPlan calculators are built to be transparent and educationally useful. Every result shown is derived from a well-known financial formula applied to the inputs you enter — nothing more, nothing less. There is no proprietary black box. The formulas and assumptions are documented below so you can verify and understand every number.
All results are estimates. Returns are assumed to be constant at the rate you enter. Real-world results vary because of market volatility, fee structures, tax changes, product rule changes, timing of cash flows, and individual circumstances.
SIP (Systematic Investment Plan)
The SIP calculator uses end-of-period monthly compounding. Each monthly contribution earns interest from the month it is invested. The formula for the future value of a regular SIP is:
FV = P × [(1 + r)ⁿ − 1] / r × (1 + r)
Where P is the monthly investment, r is the monthly return (annual rate ÷ 12), and n is the total number of months.
For step-up SIPs, the monthly contribution increases at the start of each new year by the step-up percentage you enter. The projection is built month by month using this compounding contribution.
Key assumptions: The annual return rate is constant for the full duration. Monthly investments are made at the end of each month. There are no withdrawal charges, exit loads, tax deductions, or fund management fees applied.
Known limitations: Actual mutual fund returns are not linear. Step-up assumes the increase happens exactly once per year. Results do not account for LTCG tax, STCG tax, dividend tax, or expense ratios.
Lump Sum investment
The lump sum calculator applies standard annual compound interest:
FV = P × (1 + r)ⁿ
Where P is the principal amount, r is the annual return rate (as a decimal), and n is the number of years.
Key assumptions: The entire amount is invested on day one. The return rate is constant and compounded annually. No partial withdrawals are made during the period.
Known limitations: Does not account for taxes on capital gains, exit loads, or fund-specific charges.
Recurring Deposit (RD)
The RD calculator uses the same monthly compounding formula as the SIP calculator, treating each monthly deposit as a fresh contribution that earns compound interest from the month of deposit.
Key assumptions: Monthly deposits are equal and made at the end of each month. The interest rate is constant for the full tenure. In practice, bank RD interest is typically compounded quarterly — this calculator uses monthly compounding as a simplification that may slightly overstate results.
Known limitations: Actual RD maturity amounts will differ based on the compounding frequency used by your specific bank (usually quarterly). TDS on interest is not deducted.
PPF (Public Provident Fund)
The PPF calculator compounds interest annually:
Balance (Year N) = (Balance (Year N−1) + Annual Deposit) × (1 + r)
Where r is the annual PPF interest rate you enter.
Key assumptions: The deposit is made at the start of each year (before interest is applied for the year). The interest rate is constant. The PPF annual deposit limit is Rs. 500 to Rs. 1,50,000 — the calculator enforces this range.
Known limitations: The actual PPF interest rate is set by the Government of India each quarter and can change. This calculator uses a fixed rate for the full projection. It does not model partial withdrawals, loan against PPF, or account extension beyond 15 years (though extended durations can be entered for planning purposes).
Sukanya Samriddhi Yojana (SSY)
The SSY calculator works similarly to PPF — annual compounding on deposits made during the deposit phase, followed by continued compounding through to maturity without new deposits:
- During deposit years: contribution is added before interest is applied each year.
- After deposits stop: the balance continues to compound at the same rate until the maturity year.
Key assumptions: Deposits are made at the start of each year. The rate is constant. The SSY deposit limit of Rs. 250 to Rs. 1,50,000 per year is enforced. Maturity year must be at least as long as the deposit period.
Known limitations: The SSY interest rate is revised by the government periodically. Actual maturity depends on the opening date of the account and the child's age. Tax treatment (Section 80C, EEE status) is not modelled.
EMI & Loan calculator
The EMI calculator uses the standard reducing-balance EMI formula:
EMI = P × r × (1 + r)ⁿ / [(1 + r)ⁿ − 1]
Where P is the loan principal, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of monthly payments.
For prepayment scenarios, the calculator simulates a month-by-month amortisation where a fixed extra amount is applied each month in addition to the EMI. It tracks how many months until the balance reaches zero and estimates the total interest saved.
Key assumptions: The interest rate is fixed for the full tenure. EMI payments are made at the end of each month. Prepayments are applied monthly (not as lump sum foreclosures). No prepayment penalties are applied.
Known limitations: Floating-rate loans will have EMI or tenure changes when rates change. Processing fees, GST on interest, insurance charges, and other lender-specific costs are not included. Actual lender prepayment rules may differ.
Loan Amortisation Schedule
The amortisation calculator uses the same EMI formula and builds a month-by-month schedule showing how much of each payment goes to interest and how much to principal reduction. The schedule is rolled up to an annual view for readability.
Key assumptions: Fixed rate for the full term. Equal monthly payments. No changes in tenure or rate mid-loan.
EPF (Employees’ Provident Fund)
The EPF calculator uses monthly compounding of both existing balance and ongoing contributions:
Each month, the current balance earns one month of interest (annual rate ÷ 12), and then the combined employee + employer monthly contribution is added.
Key assumptions: Monthly contributions are fixed throughout. The interest rate entered is constant. The EPF interest rate is declared annually by the EPFO — it has historically ranged between 8% and 9.5%.
Known limitations: Actual EPF calculations involve specific rules for VPF, EPS (pension component), and the distinction between employee and employer share eligible for interest. This calculator treats the total monthly input as one combined contribution for simplicity. Withdrawals, transfers, and claim conditions are not modelled. Tax implications on withdrawal are not applied.
NPS (National Pension System)
The NPS calculator uses the same monthly compounding contribution model as the EPF calculator, treating your monthly NPS contribution as a regular addition to the growing balance.
Key assumptions: The return rate entered is assumed constant (NPS returns depend on asset allocation across Tier I equity, corporate bond, and government securities funds, which vary). No charges, fund management fees, or annuity calculations are applied.
Known limitations: NPS corpus at age 60 requires a minimum 40% annuity purchase — the annuity income itself is not projected here. Actual NPS returns depend on the asset mix chosen and market performance. Tax benefits under Section 80CCD(1B) are not shown.
SWP (Systematic Withdrawal Plan)
The SWP calculator simulates a corpus that earns monthly interest and pays out a fixed withdrawal each month:
Each month: balance grows by one month of return, then the withdrawal amount is deducted. The simulation stops when the balance reaches zero or the selected duration ends.
Key assumptions: Returns are constant at the entered annual rate, compounded monthly. Withdrawals are fixed and happen at end of month. No taxes on withdrawals are applied.
Known limitations: Real-world SWP from mutual funds involves sequence-of-returns risk — poor returns early in the withdrawal phase can deplete a corpus much faster than a constant-return model shows. This calculator may overstate how long a corpus lasts.
Gratuity
The gratuity calculator uses the statutory formula under the Payment of Gratuity Act, 1972:
Gratuity = (Last Drawn Monthly Salary × 15 × Years of Service) ÷ 26
Where 15 represents 15 days of salary per year of service, and 26 represents the number of working days in a month.
Key assumptions: The salary entered is the last drawn basic + DA (dearness allowance). The calculation applies to organisations covered under the Payment of Gratuity Act (10 or more employees). Completed years of service are used — partial years are not rounded up.
Known limitations: Gratuity is capped at Rs. 20 lakh under the current Act (this cap is not enforced by the calculator, so results above this should be interpreted accordingly). Some organisations use different gratuity formulas. Government employees may follow separate rules. Tax exemption limits on gratuity are not applied.
Home Loan Prepayment
This calculator simulates the effect of making a lump-sum prepayment towards an existing home loan. It recalculates the outstanding balance after the prepayment and recomputes the remaining EMI schedule with the original EMI, estimating the reduction in total tenure and interest saved.
Key assumptions: The prepayment is applied fully to the outstanding principal. The original EMI amount is maintained after prepayment (tenure reduces). No prepayment penalty is assumed.
Known limitations: Some lenders allow borrowers to reduce EMI instead of tenure — this option is not modelled. Floating-rate changes after prepayment are not reflected.
Goal Planning & Retirement Planning
These planning calculators combine inflation-adjusted target amounts with SIP future-value projections to estimate whether existing investments are on track and what additional monthly investment may be needed.
The inflation-adjusted target is calculated as:
Future Cost = Current Cost × (1 + inflation rate)ⁿ
The monthly SIP required to reach a target corpus uses the reverse of the SIP future-value formula, solving for the monthly payment P.
Key assumptions: Inflation and return rates are constant. No existing investment growth is assumed unless explicitly entered. Tax on returns is not applied.
Inflation-adjusted present value
Many calculators show an "inflation-adjusted" figure alongside the nominal result. This converts a future maturity amount back to today's purchasing power:
Present Value = Future Amount ÷ (1 + inflation rate)ⁿ
The default inflation rate used is 6%. You can adjust this directly on any result that shows the inflation note. Your preference is saved in your browser for the session.
Financial Health Check
The Financial Health Check uses ratio-based benchmarks common in personal finance planning. These include:
- Savings rate — monthly savings as a percentage of take-home income
- EMI-to-income ratio — total monthly loan payments as a percentage of income (a ratio above 35–40% is typically considered high)
- Emergency fund coverage — months of monthly expenses and EMI covered by liquid savings
- Investment rate — monthly investments as a percentage of income
These benchmarks are simplified rules of thumb. They do not replace a full financial review and vary significantly based on individual circumstances, income stability, family structure, and financial goals.
General limitations across all calculators
- All return rates are assumed constant. Real returns fluctuate.
- Taxes on returns, dividends, or withdrawals are not deducted unless explicitly stated.
- Fund charges, expense ratios, management fees, and brokerage are not applied.
- Inflation affects all long-term projections — use the inflation-adjusted figure as a more realistic planning anchor.
- Government scheme rates (PPF, SSY, EPF) are revised periodically and the entered rate may differ from the current or future actual rate.
- All currency values are in Indian Rupees (Rs.).
Questions or corrections
If you spot an error in a formula or find a result that does not match your expected calculation, please contact us. We take accuracy seriously and will review any reported discrepancy promptly.