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Real-World Maths

True Cost Calculator

The headline price is rarely what you actually pay. Add up every extra, fee and add-on to find out what something really costs — and how far above the advertised price you end up.

TRUE COST CALCULATOR

£
Item / fee Cost each Qty

Step-by-step solution

True Cost Calculator Explained

Core concepts, classroom applications, and plain-English explanations for all audiences.

When would you actually use this?

Every time an advertised price looks too good. A £29 flight becomes £89 after a luggage fee, seat selection, airport transfer and a meal. A "free" phone on a £35/month plan costs £840 over 24 months. The true cost calculator adds up everything you'll actually pay.

Worked example

"Phone advertised as 'free' on a £32/month contract for 24 months, plus a £10 upfront fee."

Monthly cost: £32 × 24 months = £768

Upfront fee: £10

True cost: £778 total

SIM-only comparison: £10/month × 24 + £350 phone = £590

Saving by buying outright: £188

The "free phone" contract often costs 20–30% more than buying the handset separately.

Common hidden extras

  • → Flights: Luggage, seat selection, priority boarding, airport transfer — often 50–100% on top of the headline fare
  • → Hotels: Resort fees, parking, breakfast — some US hotels add 25%+ in mandatory charges
  • → Online orders: Delivery fees, return postage, subscription renewals — easy to miss until the bank statement arrives

The drip pricing problem

Drip pricing is when extras are revealed progressively during checkout, making the final price much higher than the initial advertised price. The UK's CMA (Competition and Markets Authority) has been actively challenging this practice — the maths here is a consumer protection skill.

Good to know

Why the headline price is never the whole story

Classic trap
The flight that isn't £49
Budget airlines advertise the lowest possible fare — often with no seat, no bag and no card payment included. By the time you've added the basics, you can easily pay 2–3× the headline price. Always build the full cost before comparing.
Headline: £49.00
Seat: £14.99
Checked bag: £32.00
Priority: £9.99
Card fee: £5.00
True cost: £110.98 (+126%)
Hotel resort fees
Many hotels — particularly in the US — charge a mandatory "resort fee" on top of the room rate. This covers amenities like the pool or gym whether you use them or not, and is often not shown until checkout. A £80/night room with a £25 resort fee is really £105/night.
Room (7 nights): £560
Resort fee × 7: £175
Parking × 7: £84
True cost: £819 (+46%)
The cost over time
For ongoing costs — car ownership, a phone contract, a new appliance — multiply the monthly cost by 12 or 36 to see what it really costs. A "cheap" £35/month phone deal over 24 months is £840 before you've paid for calls.
£35/month phone contract
× 24 months = £840
vs outright handset: £599
Contract costs £241 more
Compare total costs, not headline prices
The only fair comparison between two options is total cost. Build the full cost for each — base price plus every extra — and then compare. A slightly higher headline price with fewer extras often wins comfortably.
Option A: £120 + £60 extras = £180
Option B: £140 + £20 extras = £160
Option B is cheaper despite
the higher headline price