Investment Return Comparison Calculator

50,000 over 15 years at 6% against 9%: final values of 119,828 and 182,124, a gap of 62,296. At those figures a 3-percentage-point difference produces a gap of 1.25 times the principal over fifteen years. The same 3-point spread is worth less at lower rate levels and more at higher ones, passing one times the principal at a lower rate of about 4.3% at that fifteen-year horizon.

Sample figures

With a principal of 50,000 over a 15-year horizon, Option A at 6% and Option B at 9%, the gap works out to 62,296.21. These are the sample figures used across this page.

Which inputs matter most

Four relationships govern the result, and each is monotone across the whole range this calculator accepts. At a given pair of rates that fixes how the levers rank as the horizon lengthens; the ranking itself moves with the rates.

Principal is exactly proportional: a 1% change moves the gap by 1%, at every horizon and every pair of rates, with no exceptions.

At the sample rates Horizon is the strongest lever at short terms, and it weakens steadily whatever the rates are. Adding a year to a one-year projection lifts the gap by 115.0%; by five years that is 29.0%, by fifteen 14.8%, by forty 10.5%, settling toward the higher rate itself, 9.0% at these rates, since a distant gap is almost entirely the higher option's balance.

The higher rate strengthens without limit. A percentage point on Option B is worth 33.3% at one year, 42.9% at fifteen and 65.6% at forty, because each additional year compounds it against a longer run.

The lower rate runs the other way at the sample rates: a percentage point on Option A is worth −33.3% at one year, −29.1% at fifteen and −22.2% at forty, decaying as the higher option's balance comes to dominate the difference. The What-If cards report the sign for whatever rates are entered.

Those figures are one-percentage-point moves, the same perturbation the What-If cards use, measured at the sample rates. At 6% against 9% the higher rate overtakes the horizon lever between three and four years and the lower rate between four and five. Both crossings shift with the spread between the rates and with the level they sit at, in ways that do not reduce to either on its own, and in parts of the range the lower rate never overtakes the horizon lever at all.

What's happening under the hood

Each option compounds annually at its own rate, from the same starting balance and over the same horizon, and the reported figure is the absolute difference between the two final values. No money enters or leaves during the period.

One consequence worth naming: because both options start from the same principal, the horizon at which the lower rate catches the higher one's ending value is a fixed multiple of the original horizon. At 6% against 9% that multiple is 1.48, so a 15-year result at 9% takes just over 22 years to reach at 6%. The multiple depends only on the two rates, not on the principal or the horizon, and it holds provided the lower rate is above zero. At a flat 0% the lower option never catches up at all.

What this doesn't capture

This is a simplified model that holds its assumptions constant. Real outcomes vary with market conditions, costs, taxes, and timing, so the figure is best read as one scenario rather than a forecast.

Common scenarios for this calculator

• Comparing asset classes: a bond-weighted portfolio against an equity-weighted one, each at its own expected return over the same period
• Fee impact analysis: the same underlying return entered gross for one option and net of charges for the other, so the gap reads as the charge drag on a single return, a deliberate one-variable comparison, distinct from the basis mismatch described in the FAQ below
• Strategy comparison: an actively managed expectation against a passive one, both fee-adjusted
• Rate sensitivity: a single option entered twice, at an optimistic and a conservative return estimate, to see what the assumption itself is worth

What the result shows and does not show

Shows

The calculator models growth under constant annual returns. It displays a future value for each option, the difference between them, and that difference as a multiple of the principal.

Does not show

• Year-by-year interim values or drawdown periods
• The probability that either return assumption will be achieved
• Impact of withdrawals, additional contributions, or rebalancing
• Inflation adjustment or purchasing power in future years
• Interaction between investment volatility and personal circumstances
• Tax or regulatory treatment specific to any one jurisdiction

Educational use only

This calculator models a simplified scenario for learning purposes. Results estimate outcomes under steady-state assumptions and do not forecast actual performance.