Impact Tech Solutions · Financial Calculators
Compound Interest Calculator
Formula Reference
Lump Sum: FV = P(1+r/n)ntWith Monthly Contributions: FV = P(1+r/n)nt + PMT × [((1+r/n)nt − 1) ÷ (r/n)]
Where P = Principal, r = Annual Rate, n = Compounding Periods/Year, t = Years, PMT = Contribution per Compounding Period
Methodology, interpretation & sources
Purpose. Calculates the future value of a lump-sum investment, with optional regular monthly contributions, at a given compounding frequency.
How to use the result. Start with source data you can verify, enter values on a consistent unit and time basis, and record the assumptions used. The main inputs on this page include Initial Investment (Lump Sum), Monthly Contribution (optional), Annual Interest Rate (%), Time Period (Years), Compounding Frequency, Your Name. Re-run the calculation when those assumptions change rather than carrying an old result forward.
Decision use. Use this tool for scenario planning and comparison rather than as a substitute for professional financial advice. Financial assumptions can change the result materially, so test more than one scenario instead of relying on a single output.
Limitations. Check the time period, rate convention, compounding assumption and cash-flow timing before interpreting the result. Small changes in rates or timing can have a large cumulative effect.
Primary references. Use the current edition/version that applies to your jurisdiction and organization:
- State Bank of Pakistan (financial information)
- Investor.gov — financial calculators and investing basics
Editorial note. Prepared and maintained by Impact Tech Solutions. Editorially updated 28 September 2026. No individual professional credential is claimed on this page; high-consequence, statutory, tax, engineering or health decisions should be independently verified against the current primary source and, where required, a qualified professional.
Verification checklist before relying on this result
- Confirm the source and date of Initial Investment (Lump Sum), Monthly Contribution (optional), Annual Interest Rate (%), Time Period (Years), Compounding Frequency and keep units consistent.
- Check that zero, blank, percentage and currency entries mean what the calculator expects; do not use a placeholder value as real data.
- Repeat the calculation with a plausible low and high assumption to see whether the decision changes materially.
- Record the result together with the assumptions, not as a stand-alone number.
- For statutory, tax, engineering, health or safety decisions, compare the output with the current primary requirement and obtain competent review where required.
A calculator is most useful when it makes assumptions visible. If a small input change produces a very different outcome, treat that sensitivity as part of the decision rather than selecting only the most favorable result.