Investment Return Formulas
Total return on a lump sum:
FV = PV × (1 + r)^t
PV = initial investment | r = annual return | t = years
CAGR (Compound Annual Growth Rate):
CAGR = (Ending Value ÷ Beginning Value)^(1 ÷ Years) − 1
With annual contributions:
FV = PMT × [(1 + r)^t − 1] ÷ r
PMT = annual contribution (end of year)
Vermont example — $$12,410/year at 7%:
- After 10 years: $171,462 ($124,100 contributed)
- After 20 years: $508,754 ($248,200 contributed)
- After 30 years: $1,172,258 ($372,300 contributed + $799,958 gains)
Tax note for Vermont investors: In a taxable brokerage account, investment gains are subject to 8.75% state income tax plus federal capital gains tax (~15% for long-term). Combined rate ≈23.75%, reducing an effective 7% return to approximately 5.3% after tax. Tax-advantaged accounts avoid this drag entirely — use them first.