Calculating TV impacts from your media budget is relatively easy.

The formula is: Budget / CPT x 1,000

So, if your budget is £250,000 and your CPT is £5 then you are buying 50,000 thousands of impacts or 50,000,000 impacts.

In TV media planning these calculations are usually based on a 30 second ad. But what happens if you are running a different time length?

TV time-length factors

When you are running different time lengths you have to weight the budget to account for the fact that you are buying more or less time in the ad break. You then use this weighted budget to calculate your impacts. The weighting factors are as follows:

• 60 seconds = divide your budget by 2 (as you are buying twice the length of a 30 second ad.
• 40 seconds = divide by 1.33
• 30 seconds = divide by 1
• 20 seconds = divide by 0.85
• 10 seconds = divide by 0.5

This means that if you are running a 60 second ad your £250k budget has to be considered a £125k budget for the purpose of calculating your media impacts. Likewise if you are planning for a 10 second ad, your budget is worth £500k for the purpose of calculating impacts.

Understanding time-length cost efficiencies

You should notice that in the factors above the weightings do not always match the relationship to 30 seconds. For example, 10 seconds is only 33% of 30 seconds but the time length factor charged by TV contractors is 0.5. This means you are paying a 50% cost weighting premium to run a 10 second ad vs a 30’second ad.