# How to calculate an overall 5 star rating based on other weighted 5 star ratings

I have these 3 ratings. I want to combine them to produce an overall rating out of 5. The overall rating can be a float, so no rounding is necessary, but it cannot be negative. I'm just not sure how to do it.

Technical Rating from 1 to 5, weighting 2:1 (i.e A rating of 5 equals 10)

Production Rating from 1 to 5, weighting 1:1

Content Rating from 1 to 5, weighting 3:1

Any hints or advice would be awesome, thanks.

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Good clear description of your question. –  André Nicolas Sep 19 '12 at 22:40
@AndréNicolas Thanks! Sadly, I've had a lot of practice asking questions! ;) –  MFB Sep 20 '12 at 0:10
If you need something more elaborate try some fuzzy inference mechanism (fuzzification/defuzzification). Every rating values induces a fuzzy set accompanied by a membership function. But, I think the answer by Henry should be sufficient for most applications. –  Pantelis Sopasakis Sep 20 '12 at 0:17

You could try something like $$\frac{2TR + PR + 3CR}{6}.$$

Try it with various examples including

• $(5,5,5)$ to give a result of $5$,
• $(1,1,1)$ to give a result of $1$,
• $(4,1,1)$ to give a result of $2$,
• $(1,4,1)$ to give a result of $1.5$,
• $(1,1,4)$ to give a result of $2.5$,

to see the effect.

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I have a smallish brain, so I really don't get how this works, but it does. Thank you!! –  MFB Sep 20 '12 at 0:19
It is called a weighted average and uses your weights. Note that $2+1+3 = 6$. –  Henry Sep 20 '12 at 6:34