Help with math/figuring prices, please....

BrandNewDay

I do take a calculator to the store with me. And, I'm about to make a notebook where I keep track of good prices. Like, what is the standard price of cheese per kilo, what's the cheapest I've seen, and then I can do the math to see if the deal at the store is really such a deal that I ought to stock up. Does that make sense?

Anyway, I have problems, sometimes, doing the math. Generally, I like to have the price per kilo (or liter.) It gets tricky when it's cheese in portions of 245 grams and the deal is something like 3 for £4. OK... that's 735 for £4. How does that compare to my target of < £5 a kilo?

It's also hard when the amounts are over a kilo. If it's chicken breasts 1275 grams for £5, I have to REALLY think about it. My goal is to beat £4 a kilo. I cannot do this while pushing a grabby baby in a trolley. I need to have basic formulas written down in my notebook that I can just punch it in to my calculator.

Can anybody help me to come up with formulas I can write down and just use in a hurry, while distracted?

albertross_2

divide £4 by 735 then multiply by 1000 (£5.44/kilo)

divide £5 by 1.275 (£3.92/kilo)

or shop online/look at the offer smallprint, and look at the price per gram.

It's easier if you compare prices per gram.

patchwork_cat

Ok was about to say maths not math when I read you sig!I second the online, but not possible if Aldi or Lidl. Just write down your prices either on a recci mission or whilst just doing a shop, then sit down at home and compare against online- that is the best way I find. Also I cheat by taking my daughter and she writes prices as I feel a right one walking around the shop with pen, paper and calculator.

Penelope_Penguin

I estimate things in my head:

BrandNewDay wrote: »

Anyway, I have problems, sometimes, doing the math. Generally, I like to have the price per kilo (or liter.) It gets tricky when it's cheese in portions of 245 grams approx 1/4 kilo and the deal is something like 3 for £4. OK... that's 735g approx 3/4 kilo for £4. How does that compare to my target of < £5 a kilo?

It's also hard when the amounts are over a kilo. If it's chicken breasts 1275 grams approx 1 1/4 kilo for £5, I have to REALLY think about it. My goal is to beat £4 a kilo. I cannot do this while pushing a grabby baby in a trolley. I need to have basic formulas written down in my notebook that I can just punch it in to my calculator.

Can anybody help me to come up with formulas I can write down and just use in a hurry, while distracted?

HTH, Penny. x

Ben84

I believe they have to list the price per unit (for example Kg) in store. In Sainsburys I always find it on the shelf with the price, but it is very small and you have to look closely.

However, this price is often before the offer or multi-buy discount. So, I sometimes encounter the problem you're having.

The method I use is to divide the cost in pence (never pounds) by the weight in Kg. I do use a decimal place for the Kg, if needed. For example 300g would be 0.3 Kg.

For an example, if 500g packets of butter are £1.49:

149 / 0.5 = 298

This should always gives the cost in pence per Kg.

BrandNewDay

yes! The problem only happens when it's a special offer.
I think weight per gram may be a better idea than kilo, becuase then I don't have to convert to kilos and back. thanks for that.

What happens if I divide the cost in pence by grams? Huh... let me see....OK. you get .298 which I guess is how many pence per gram. At any rate, so long as I keep it allll consistent (always pence/gram) it should work.Right?

So, if it's a multibuy special:

Cheese. 265 grams per item. 3 for £6. Then:

265 x 3= 795 grams for 600 pence
600/795 = .754 pence per gram.

My target price is £5 per kilo, or 500 (pence)/1000 (grams) = .5 pence per gram.

So, .75 pence is 50% more than .5 pence and that is no savings at all!

OK... must write this down:

pence/grams = pence per gram

Thank you!

Ben84

Pence per gram will work fine the way you're doing, it's just a matter of where you put the decimal place and always finds the exact same number. However, I slightly prefer pence per Kg as that's how they usually list prices in store and on-line, so it gives me a number that I can use directly against the others without having to calculate them too.

BrandNewDay

Ben84 wrote: »

Pence per gram will work fine the way you're doing, it's just a matter of where you put the decimal place and always finds the exact same number. However, I slightly prefer pence per Kg as that's how they usually list prices in store and on-line, so it gives me a number that I can use directly against the others without having to calculate them too.

I think grams works better because it's always easy to convert kilograms to grams, but not always easy to convert grams to kilograms. Well, of course it is, in some sense. 650 grams is .65 kg. But, if I'm comparing £3 per kg to £2.5 per 645 grams, it's just easier to convert and compare everything on a pence-per-gram basis, IMO.