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Finance Tools

These tools handle the arithmetic behind financial decisions: what a loan actually costs over its term, how savings grow when interest compounds, and where a business's margins sit. Because the numbers here can influence real decisions, every calculator states its formula, lists what it holds constant, and is explicit about the difference between a calculation and advice. None of them are a substitute for a qualified adviser.

All finance tools

How these are grouped

Mortgages
Repayment, interest and amortization for property loans.
Loans
Business and personal borrowing costs over a fixed term.
Savings & investing
How balances grow with compounding and contributions.
Business
Margin, markup and return calculations for operators.

Choosing the right tool

Reach for the Mortgage Calculator when the question is about a single property loan and its monthly payment. Use the Business Loan Calculator instead when a fee is involved — arrangement or origination fees change the real cost enough that they need their own comparison, which the mortgage tool doesn't model. The Compound Interest Calculator answers a different question entirely: not "what does borrowing cost" but "what does saving or investing regularly grow into". The Profit Margin Calculator is unrelated to borrowing altogether — it's for pricing a product or service, and its most useful feature is converting between margin and markup, which are not the same number.

Common mistakes

  • Quoting a markup percentage as if it were a margin percentage — a 100% markup is only a 50% margin, and the two get mixed up constantly in pricing conversations.
  • Comparing loan offers on interest rate alone, ignoring arrangement fees — a lower rate with a high upfront fee can cost more than a higher rate with none, especially over a short term.
  • Assuming compounding frequency barely matters — it matters far less than people expect at typical savings rates, but the rate and the contribution size matter a great deal, and conflating the three leads to bad projections.
  • Treating a mortgage calculator's fixed-rate output as what a real quote will be, when most mortgages fix for an initial period and then move to a variable rate the calculator doesn't model.

A short example

A small business owner is deciding whether to take a £50,000 loan with a 2.5% arrangement fee at 8.9%, or a fee-free offer at 10.4%, and separately wants to check their planned selling price gives a 40% margin.

The loan comparison isn't decided by the headline rate — it needs the fee measured against what actually reaches the account (see the loan-fees guide below). The pricing question is separate and needs the reverse-margin calculation: price = cost ÷ (1 − 0.40), not a markup of 40% on cost, which would under-price the item relative to the target.

Finance guides

Frequently asked questions

Are these figures a substitute for financial advice?
No. Every calculator here does arithmetic on the numbers you enter, under stated assumptions — it is not regulated financial advice, a loan offer, or a decision in principle. Speak to a qualified adviser before making a borrowing or investment decision.
Why do two mortgage calculators sometimes give different monthly payments for the same numbers?
Usually a rounding or day-count difference, or one tool including fees, insurance or taxes that another excludes. This one states its assumptions explicitly above each result specifically so the figure can be checked against another source.