Calculator Comparisons
Examples reviewed 15 September 2026. Calculated from the same engines used by the linked tools.
Each comparison sets two options against the same inputs, states every assumption in the open, and then hands over to the calculator that can run your own figures. They exist because the honest answer to most either-or money questions is "it depends on the numbers you have not told me yet", and a worked example is the fastest way to see which numbers those are.
Start with a worked example, inspect its assumptions, then follow the calculator link to enter your own figures.
- 15 vs 30 Year Mortgage: Payments, Interest and Remaining Debt
Compare a 15-year and 30-year mortgage with the same principal and rate, including payment, lifetime interest and five-year borrowing cost.
- SIP vs Lump Sum: Equal Contributions, Different Investment Timing
Compare monthly SIP contributions with an upfront lump sum, using the same total invested and explicit assumptions about returns and timing.
- Plan 2 vs Plan 5 Student Loan Repayments
Compare UK Plan 2 and Plan 5 repayment thresholds, monthly estimates and cancellation horizons with sourced 2026/27 assumptions.
How to read a comparison
Each worked example holds everything constant except the one choice being compared: the same loan amount and rate for the two mortgage terms, the same total invested for SIP and lump sum, and the same salary and balance for the two student loan plans. That is what makes the difference in the result attributable to the choice itself rather than to a change in the inputs.
The examples use round, typical figures, so the gap you see is a direction and a rough size, not your answer. A shorter mortgage always costs less interest but needs a higher payment; an early lump sum usually beats spreading the same money out when returns are positive; and which student loan plan costs more depends on your salary and how fast it grows. Run your own numbers in the mortgage comparison calculator, the compound interest calculator or the UK student loan repayment calculator.