Why the "real" number is the only one that matters
A 7% return with 3% inflation is not a 7% return. It's a 3.88% real return, compounded. Over 30 years, the gap between $1 nominal and $1 real is enormous. The chart above deliberately pushes you to read the real line as the truth and treat the nominal as a vanity number. Tax drags it further. Sequence-of-returns risk and contribution timing aren't shown here but are why the same math with two real investors produces two very different outcomes.
FAQ
Why is "annuity-due" larger than "ordinary annuity"?
Because each contribution earns one more period of compound interest when it's deposited at the start of the period instead of the end. If your paycheck is auto-deposited on day 1 of the month, you're already living in annuity-due land — many calculators under-report your actual balance because they assume the ordinary case.
Why not just use 7% inflation-adjusted instead of showing three lines?
Because tax is real money you owe, not a discount rate. Treating it as a reduction in the return hides the actual number you'll have in your brokerage account vs what you'll be able to spend. The three lines let you see all three amounts separately so you can plan against the right one.
Does this handle tax-deferred vs taxable accounts differently?
No. This calculator applies a flat annual tax rate on gains. For tax-deferred accounts (401k, traditional IRA in the US; SIPP in UK), set the tax to 0 and treat the projection as gross. For Roth-style accounts, the contribution is post-tax and the growth is untaxed — also set tax to 0, but recognize the contributions themselves were already taxed at the marginal rate.
Methodology
Future value with periodic contributions: FV = P(1+r)n + C × ((1+r)n − 1)/r, adjusted for contribution timing. Real value = Nominal ÷ (1+inflation)years. After-tax = Nominal − (Nominal − principal_contributed) × tax. The compound rate is divided by the cadence count (monthly = r/12, weekly = r/52, etc.). Source: standard finance textbook formula, identical to the formulation in Bodie, Kane & Marcus.