Our Methodology
How SmartMoney77 calculators work, where our data comes from, and what to verify independently
SmartMoney77 calculators are built on standard financial models and publicly available data. This page explains how each category works, where the data comes from, and what you should verify independently before making financial decisions.
How Our Calculators Work
- Financial Planning Calculators — Compound Interest, FIRE, Killer Fees, Latte Factor, and others use standard financial formulas: compound interest with monthly contributions, the 4% safe withdrawal rate for FIRE, and fee-adjusted growth projections. All calculations happen in your browser — we never store your financial inputs.
- Stocks & Indices — S&P 500, Nasdaq 100, Nvidia, Tesla, Apple, and other stock calculators use historical split-adjusted daily closing prices from Yahoo Finance. When you enter "What if I invested ₹8,30,000 in Nvidia 5 years ago?", we use the actual adjusted closing price on that date and calculate total return in USD. Results are converted to your selected currency using current exchange rates.
- Crypto — Bitcoin, Ethereum, and Solana calculators use historical price data from CoinGecko's API. Prices are in USD. We do not model staking rewards, gas fees, or exchange fees. Results show pure price appreciation of buy-and-hold.
- Commodities — Gold, Silver, and Oil calculators use price data from Yahoo Finance commodity tickers. Gold and silver prices are per troy ounce in USD. Oil uses WTI crude. We do not model storage costs, ETF expense ratios, or futures contract rollovers.
Data Sources & Update Frequency
- Stock & index prices
- Yahoo Finance (split-adjusted closing prices). Updated daily.
- Crypto prices
- CoinGecko API. Updated daily.
- Commodity prices
- Yahoo Finance commodity tickers. Updated daily.
- Exchange rates
- open.er-api.com. Updated daily.
- Financial formulas
- Standard compound interest, 4% rule (Trinity Study). Static — reviewed semi-annually.
- Inflation assumptions
- User-configurable per calculator. No default inflation adjustment unless user reduces the rate manually.
Built-In Assumptions
- Returns
- Nominal (not inflation-adjusted) unless explicitly stated. To estimate real returns, subtract 2–3% from the annual rate.
- Stock prices
- Use adjusted closing prices which account for splits and dividends.
- FIRE (4% rule)
- Based on the Trinity Study. Assumes a 30-year retirement horizon with a diversified portfolio.
- Compound interest
- Assumes end-of-period monthly contributions with monthly compounding.
- Taxes
- No calculator accounts for taxes. Tax treatment varies by country, account type, and individual situation.
- Fees
- No calculator accounts for investment fees unless you're specifically using the Killer Fees calculator.
- Exchange rates
- Current-day rates are applied to historical results. We don't use historical exchange rates for currency conversion.
Known Limitations
Inflation
We show nominal returns by default. For a rough real-return estimate, subtract 2–3% from the annual rate.
Taxes
Tax impact can range from 0% (tax-sheltered accounts) to 30%+ depending on jurisdiction. Always consult a tax advisor for your specific situation.
Fees
Only the Killer Fees calculator models fee impact explicitly. Other calculators show gross returns before any fees.
Currency
Historical results are calculated in the asset's native currency (usually USD) and converted at today's exchange rate. This doesn't reflect actual currency movements over time.
Past performance
All historical calculators show what happened, not what will happen. Future returns may be significantly different from historical averages.
What You Should Verify Independently
- Fund expense ratios Fees change over time. Always verify current expense ratios on your provider's website before making decisions.
- Tax implications Tax treatment varies by country, account type, and withdrawal strategy. Consult a qualified tax advisor.
- Historical data accuracy Small differences between our data and your broker's records are normal — they may use different split-adjustment dates or data providers.
- Your actual risk tolerance No calculator can measure your emotional reaction to a 30% market drop. Consider how you'd feel — and act — during a real downturn.