How our insurance calculators work
Our approach to calculator design
Every calculator on Insurance Calculators UK is built around three commitments: transparent formulas, honest assumptions, and clear labelling of what the output is — and isn't. This page explains how each calculator category works and where the data comes from.
Published rates vs illustrative estimates
We draw a hard distinction between two types of figures:
Published rates — cited from authoritative sources
Insurance Premium Tax rates (HMRC), the IHT nil-rate band and 40% rate (gov.uk), and the employers' liability statutory minimum of £5 million (gov.uk) are all pulled from config/sources.ts rather than hardcoded inline. When HMRC or gov.uk updates a rate, we change one config value and every page that uses it is updated automatically.
Illustrative estimates — clearly labelled as not a quote
Pet insurance cost bands, travel cost bands, cyber insurance cost bands, and rebuild cost ranges are illustrative. They are anchored to published averages where these exist (ABI premium data, RICS/BCIS rebuild guidance), and every output carries a visible “Not a quote” label. These figures are stored in config/assumptions.ts so they can be reviewed and updated independently.
Car insurance calculators
The voluntary excess calculator uses a straightforward cost comparison: total cost over a period equals annual premium multiplied by years, plus excess multiplied by expected claims. The break-even is the number of claims at which the higher-excess option stops saving money. No risk scoring — the tool stays neutral and lets users reach their own conclusion.
The comprehensive vs TPFT calculator models vehicle value depreciation year by year using a compound percentage, then compares the potential own-damage exposure at each point with the premium saving from choosing the cheaper policy.
The no-claims discount calculator illustrates the monetary value of a discount by comparing total cost across scenarios (no claim, one claim, two claims) with and without protected NCD. Insurer rules vary; the tool states this clearly and does not pretend to reproduce any specific insurer's step-back scale.
Life and protection calculators
The life insurance needs calculator totals the components of financial need (income replacement, mortgage, other debts, children's costs, funeral/estate expenses) and subtracts existing assets (savings, existing cover). Income replacement need accounts for a partner's income contribution to avoid over-estimating. The final figure cannot fall below zero.
The mortgage protection calculator models the outstanding loan balance over time using the standard amortisation formula: B(n) = P × [(1+i)^N − (1+i)^n] / [(1+i)^N − 1], where P is the loan, i is the monthly interest rate, N is the total number of months, and n is the month in question. This generates the decreasing cover schedule used in the level-vs-decreasing comparison.
The income protection calculator derives the monthly gap between desired income and available support (employer sick pay, state benefits, existing protection). Note: income protection premiums are exempt from Insurance Premium Tax — the calculator flags this.
The life insurance in trust estimator uses the current IHT rate (40%) and nil-rate band (£325,000) from config/sources.ts. It illustrates the potential IHT saving if the policy sum assured is kept outside the estate in trust. It does not model the full estate — it only estimates the potential saving on the policy payout itself.
Home insurance calculators
The rebuild cost calculator uses broad £/m² ranges by region and build quality, anchored to RICS/BCIS guidance, with multipliers for property type. It returns a low–high range rather than a single figure, because rebuild costs vary significantly. The ranges are stored in config/assumptions.ts and are clearly described as estimates — a professional assessment from a RICS-accredited surveyor gives the most reliable figure.
The contents calculator uses default values by bedroom count and quality tier (from config/assumptions.ts) and adds user-supplied values for specific categories. It produces a total for review, not a recommended sum insured, and includes a reminder about high-value items that may need separate specification.
The underinsurance calculator applies the average clause formula: potential payout = claim amount × (sum insured ÷ true value). This is the standard application of the condition of average. The tool explains that whether the clause applies depends on actual policy wording.
Pet insurance calculators
The pet insurance cost estimator applies a weighted model to published average monthly premiums, adjusting for pet type, age, breed size, cover type, vet-fee limit, and region. All weights are in config/assumptions.ts. The output is clearly labelled “not a quote” — pet insurance pricing is highly individual and affected by factors this tool does not collect (such as the specific breed, postcode, and insurer).
We do not ask for animal medical history or pre-existing conditions in any pet calculator. These tools are for cost and structure comparisons only.
Business insurance calculators
The business interruption calculator estimates the total indemnity period exposure as monthly gross profit or fixed costs multiplied by recovery months, plus payroll and increased cost of working. The tool makes no assumptions about the cause of the interruption or policy triggers — those are policy-wording questions.
The public liability calculator does not risk-score the business. It shows how different cover limits compare against an example claim value and flags contractual minimum requirements. The employers' liability statutory minimum of £5 million is cited from gov.uk.
Travel insurance calculators
The travel insurance cost estimator applies destination-region base prices with multipliers for trip length, traveller age, add-ons (winter sports, cruise, business travel), and policy type (single-trip vs annual). Base prices are sourced from published market data and stored in config/assumptions.ts. We do not ask for medical details — pre-existing conditions are a key underwriting factor that makes real quotes essential.
The cancellation cover calculator simply totals prepaid costs and subtracts the refundable element to show the amount genuinely at risk. It flags that cancellation cover only applies from the policy start date — a reason to insure as soon as you book.
Insurance Premium Tax calculator
The IPT calculator uses rates set by HMRC: standard 12% for most general insurance, higher 20% for certain travel and mechanical cover, and 0% for exempt policies (life insurance, income protection, commercial ships and aircraft). Both add and extract modes are available.
Questions about a specific calculator?
Every calculator page includes an “Assumptions and methodology” section that explains the formula used, the data sources, and any limitations. If you think a figure is wrong or an assumption should be updated, contact us.
Frequently asked questions
Insurance pricing depends on individual underwriting factors that a public calculator cannot and should not model — medical history, driving record, credit checks, exact property details. Showing a range is more honest than a false-precision single number. We label ranges clearly as illustrative.
We review the published rates (IPT, IHT, employers' liability minimum) when HMRC or gov.uk update them. Illustrative bands and rebuild cost data are reviewed at least annually. Every page shows a 'last reviewed' date.
You don't need to register or share your details to get value from these tools. We believe privacy-friendly design is a feature, not an afterthought.
No. All outputs are general estimates for information purposes only. Nothing on this site creates an advisory relationship, and no result should be treated as a quote or a recommendation. Speak to a regulated broker or adviser for decisions specific to your situation.
Related calculators
Car insurance
Voluntary Excess Calculator
Compare the cost trade-off between lower and higher voluntary excess on car insurance.
Life insurance
Life Insurance Needs Calculator
Estimate how much life cover your family might need based on income, mortgage, and debts.
Home insurance
Underinsurance Calculator
Check whether your sum insured may leave you underinsured and estimate the potential shortfall.
Disclaimer
This is a simplified estimate based on the assumptions shown above. It isn't a quote, and a real insurer may arrive at a different figure. Use it as a starting point, then check the details with your insurer or adviser.