Methodology
How MotorCrunch turns your inputs into a number — the standard formulas we use, where our default assumptions come from, and how we keep them current. Every figure here is an estimate, not a quote.
Last reviewed: 2026
Assumptions are shown on every page
Our core principle is that there are no hidden defaults. Every rate, term, price and cost assumption a calculator uses appears on screen and can be edited. When you change an input, the result recalculates with the same transparent formula — so the number always reflects the assumptions you can see, not a black box.
This matters because a car-money decision is only as good as the assumptions behind it. We would rather show our work and let you adjust it than present a single confident figure you cannot inspect.
The formulas we use
MotorCrunch calculators run on documented, industry-standard math — the same equations a lender, actuary or energy analyst would use. None of it is proprietary scoring.
Loan amortization
Monthly payments, total interest and the running balance use the standard amortization formula — the same closed-form equation a lender uses to price a fixed-rate loan from principal, annual rate and term.
M = P · r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where r is the monthly rate and n the number of payments.
Compounding depreciation
Resale value and total cost of ownership use a compounding depreciation curve: value falls by a percentage each year rather than a flat amount, which matches how vehicles actually lose value by class and age.
Value(t) = Price · (1 − d)ᵗ, with d calibrated to published cost-to-own data by segment.
Fuel & energy cost models
Running costs combine distance, efficiency and a per-unit price. Petrol and diesel use consumption per distance times fuel price; EVs use kWh per distance times an electricity tariff, with optional public-charging premiums.
Annual cost = (distance ÷ efficiency) · unit price, per fuel or energy type.
Insurance multiplier model
Insurance estimates start from a regional base premium and apply transparent multipliers for factors such as vehicle class, driver profile and coverage level. It is a directional estimate, never an underwritten quote.
Estimate = base premium · (factor₁ · factor₂ · …), each factor disclosed on the page.
Where our assumptions come from
Default values — fuel and electricity prices, insurance cost indices, vehicle valuations, depreciation rates and cost-of-ownership figures — are based on published government and industry sources where available. We list each publisher, with a link and a last-checked date, on our Data Sources page.
Where a precise figure is not published for a given market, we use a clearly labelled, conservative assumption derived from the nearest comparable public data, marked as an estimate rather than a precise figure. You can always override it with your own quoted numbers.
How figures are reviewed and updated
We re-check default assumptions against their published sources on a recurring schedule and update them as the underlying data moves. Each source on the Data Sources page carries its own last-checked date so you can see how current a given input is. Our country and city assumptions were last reviewed in 2026.
Calculator formulas themselves are pure, typed and unit-tested, so a change to an assumption never silently changes how the math works.
What the numbers are — and are not
They are
- Educational estimates from standard formulas.
- Built on transparent, editable assumptions.
- Useful for comparing scenarios before you commit.
They are not
- Real-time prices or live market quotes.
- Binding quotes from a lender, insurer or dealer.
- Personalized financial, insurance, tax or legal advice.
See our Disclaimer for the full scope and limitations.
Methodology FAQ
Are MotorCrunch figures real quotes?＋
No. Every number is an estimate produced by a standard formula applied to the inputs and assumptions shown on the page. It is not a quote from a lender, insurer or dealer, and it is not personalized financial advice. For a binding figure, ask a regulated provider for a real quote.
Where do the default assumptions come from?＋
Defaults are based on published government and industry data where available — fuel and energy prices, insurance statistics, vehicle valuations and cost-of-ownership studies — listed on our Data Sources page; where a precise public figure is not available we use clearly labeled, conservative estimates. Because every input is editable, you can replace any default with your own real numbers.
How often are the numbers updated?＋
We review default assumptions against their published sources on a recurring basis and refresh them as the underlying data changes. Each source carries a last-checked date, and our country and city figures were last reviewed in 2026.
This page explains how our estimates are produced. It is not financial, insurance, tax or legal advice. Verify any figure with a qualified provider before making a decision.