The formulas, in plain language
ROI % = (Final value − Initial investment) / Initial investment × 100
Annualized return % = [(Final value / Initial investment)^(1/years) − 1] × 100
Worked example
Suppose you invested $10,000 and it's now worth $16,000, over 4 years:
- Net gain: $16,000 − $10,000 = $6,000
- ROI: $6,000 ÷ $10,000 × 100 = 60%
- Annualized return: (16,000/10,000)^(1/4) − 1 = about 12.47% per year
The 60% figure is the total return over all 4 years combined; the 12.47% figure is what that same growth looks like spread evenly across each year — useful for comparing against, say, a savings account's annual rate.