Trading & Investment Calculators

What is a position size calculator?

A position size calculator works backwards from the loss you're willing to take on a trade. You enter your account size, the percent of it you'll risk (typically 0.5-2%), the entry price and the stop-loss price; the tool divides your risk amount by the per-unit stop distance to return the exact number of units to buy. Done right, a hit stop loses exactly your chosen risk, regardless of how wide the stop is — leverage doesn't change that, it only changes the margin you post.

How do I calculate ROI?

Return on investment is Net Profit ÷ Initial Investment × 100. For a stock or crypto trade, net profit is (Sell Price × Amount) − (Buy Price × Amount) − Fees. For long-horizon comparisons you also want annualized ROI: (Final ÷ Initial)^(1 ÷ Years) − 1. The ROI Calculator on FinToolbox runs both formulas live and shows the break-even price for any fee load.

What is compound interest?

Compound interest is interest earned on both your original principal and the interest that has already accumulated. Because new interest is calculated on a growing balance each period, returns become exponential rather than linear over long horizons — the second decade of a long investment typically contributes more than the first. The Compound Interest Calculator visualises the crossover between your contributions and the interest the chart of which dominates over time.