Our methodology
How we create estimates, what assumptions we make, and why results are illustrative rather than quotes.
How estimates are created
Each calculator applies a transparent formula to the inputs you provide. The formula and its key assumptions are shown in a “Methodology” box on each calculator page, so you can see exactly how the result was reached.
Where a figure is taken from an authoritative source (HMRC, ABI, gov.uk, RICS/BCIS), we cite the source on the page. Where we use a rule of thumb or an illustrative band, we label it clearly and keep the values in config files so they can be updated when new data is available.
Why assumptions are simplified
Real insurance pricing involves hundreds of variables, risk models, and underwriting rules that are confidential to each insurer. A calculator that pretends to replicate this process would be misleading. Instead, we focus on the key variables that genuinely affect the outcome and are within your control.
For cost estimators (pet, travel, cyber), we use illustrative bands anchored to published averages where they exist. We label these clearly as “not a quote” and note the factors that move real prices. Our goal is to help you understand what matters, not to simulate a quote engine.
How often assumptions are reviewed
We review assumptions at least annually, and update them when published rates change (for example, when HMRC changes IPT rates) or when new ABI data becomes available. Each calculator shows a “last reviewed” date so you can see how recent the review was.
Why results aren't quotes
These calculators produce general estimates based on simplified assumptions. A real insurer assesses individual risk factors, credit data, claims history, policy terms and exclusions, and many other variables that we neither collect nor model. Any output from this site is a starting point for your thinking — not a quote, and not a guarantee of what you would be charged.
For any significant insurance decision, speak to your insurer directly or use a regulated broker or qualified financial adviser who can assess your specific circumstances.
Category-specific methodology
Car insurance calculators
Car calculator outputs are based on user-supplied premium figures, not estimated market rates. The voluntary excess and no-claims discount calculators use the user's own insurance costs, so accuracy depends on what the user enters. Illustrative factors and comparison logic apply.
Life and protection calculators
Life cover needs are calculated from the inputs you provide (income, mortgage, debts, savings). The mortgage protection calculator uses a standard amortisation formula for decreasing term comparison. All outputs are illustrative needs estimates, not underwriting decisions.
Home insurance calculators
Contents defaults are illustrative starting points based on household size and quality level, not a room-by-room inventory. Rebuild cost uses broad £/m² bands anchored to RICS/BCIS guidance ranges. A professional valuation is always recommended for both.
Pet insurance calculators
Pet cost estimates use a weighted illustrative model anchored to published averages where available. All cost bands are labelled as not a quote. The tool does not ask for or factor in medical history or pre-existing conditions.
Business insurance calculators
Business interruption exposure is calculated from user-supplied financial figures. Public liability comparisons show contractual minimums and coverage gap illustratively. Cyber cost bands are illustrative and labelled as such. A broker or adviser should always confirm appropriate limits.
Travel insurance calculators
Travel cost estimates use an illustrative points-based model by destination region, trip length, and traveller profile. Medical conditions can significantly affect real quotes; this tool does not ask for medical details. All bands are labelled as not a quote.
General tools
The IPT calculator uses published HMRC rates. The monthly vs annual calculator uses a standard present-value bisection method to derive an implied APR. Rates are confirmed for the current tax year and will be updated when HMRC publishes changes.