Compare pizzas and save cash. A simple tip to ’slice’ down your costs

Martin Lewis, moneysavingexpert.com.

I arrived home on Friday evening to see a flurry of pizza delivery leaflets on the mat. As is common of their type, all included deals like “buy one medium pizza, get the second half price” or “special sale on giant pizzas”. As my mind’s always worked mathematically I couldn’t help working out which the best value deals was on each leaflet; for example are two 8″ pizzas costing £11 better value than one 12″ pizza costing £10.

It’s only school maths that’s needed to do it, so I thought I’d share it here (in case you’ve forgotten). The area of a circle is πr2 and from this we can deduce a simple rule:

Easy comparison of pizzas’ areas

Simply square (multiply by itself) the diameter (width) of the pizza. While this doesn’t give you the area, as the rest of the equation for area is a constant, then you can simply use these amounts as an easy way to compare relative areas.

An example will help

Imagine the choice is the following:

A. Two 8″ pizzas cost £11
B. One 12″ pizza costs £10

At first glance the 12″ pizza doesn’t seem that much bigger, yet actually it’s much bigger. Let’s do the comparison.

A. Square 8″ and you get (8x8=) 64. Yet there are two eight inch pizzas so we must double this to get 128.
B. Then simply square 12″ and you get (12x12=) 144.

What this means is you get more pizza buying one 12 inch than buying two eight inches. To be accurate there’s (144/128=1.125) 12.5% more pizza buying the 12″, and as it’s cheaper it’s a much better deal as its cheaper anyway.

The ifs and buts

Now of course this is based on simple maths, and some (probably pizza stores) may argue there are variants. If you wanted different toppings or different bases and they won’t do half and half, size is irrelevant. You could say the 12″ pizza actually has a thicker edge and argue there’s a little less topping space and redo the calculation, yet overall this simple rule helps.

A much cheaper way to do pizza

Now the regulars in the thrift specialising Old Style section of the Chat Forum on my website MoneySavingExpert.com would shout at me if I didn’t mention that making pizza yourself is massively cheaper and much easier than ordering it!

Martin

PS. For maths nerds. For those saying “he’s used the diameter but the equation is about radius”; please remember the equation is commutative and this is not about “finding the area” but “finding the relative area” so rather than making people halve the diameter to get the radius - the proportions are the same just by squaring the radius.

Comments

[Nick Draper]

Martin,

The r in pi * r² is radius, not diameter. You need to square half of the diameter.