How the same-budget comparison works
Let P be the initial amount, C the monthly savings budget, N the common horizon and d the delay. Both scenarios save P + 12 × N × C. The delayed scenario holds P + 12 × d × C as zero-interest cash, then invests that amount for N − d years while continuing the same monthly C. A delay of N years leaves the entire budget in cash; a delay of zero produces identical scenarios.
This page uses the same fixed-return model as the S&P 500 calculator: contributions occur at the beginning of each month, return accrues on the invested balance between payments and is compounded annually. It does not use the effective monthly rate and month-end payments used by the separate savings calculator. For whole years, one year updates invested balance B to B × (1 + g) + C × (12 + 6.5 × g), where g is the annual return as a decimal.
Illustrative hand-check: P = 1,000, C = 100, N = 2, d = 1 and annual return = 12%. Starting now ends year one at 2,398 and year two at 3,963.76. Waiting saves 2,200 cash in year one and ends year two at 3,742. Both save 3,400 in total; the nominal difference is 221.76. At 10% annual inflation, that difference is 183.27 in today’s purchasing power. At zero return both end at 3,400; negative returns can reverse which balance is higher.
Results are hypothetical, educational, not financial advice and not predictions. Returns and inflation are fixed user assumptions, not market data. Cash earns zero interest. This model excludes taxes, fees, changing budgets, volatility and market timing. It does not decide whether investing is appropriate for you.