When media planners develop TV campaign plans they are often optimising the relationship between three sets of numbers:
- TVRs (or GRPs, or TRPs) – TVRs or TV rating points are a reflection a target audience using both demographics and geography. If there are 50m adults in the UK then 1 Adult National TVR is 1% of 50m – 500,000. If a national programme is watched by 2m adults it delivers 4 TVRs.
- Reach (or coverage) – Reach is the percentage of your target audience that is reached by a spot or a campaign. TVRs build reach and frequency. This is explained in more detail here.
- Average opportunities to see (OTS) – Average OTS is the number of times on average that a member of your target audience will see you ad.
There are some simple calculations to illustrate how these numbers work together. There is one thing you will need to begin this process and that is a reach curve. A reach curve looks like this:
This curve describes the relationship between TVRs and reach. It illustrates how your reach (sometimes called coverage) increases as you add more TVRs to your campaign. You will see that with each additional 100 TVRs you add to your campaign, your reach increases more slowly. In practical terms this is because some of your target audience will see you ad more than once, even in the early stages of the campaign. This is called opportunities to see or OTS.
How do we calculate OTS?
OTS is calculated by dividing your TVRs by your reach: At 300 TVRs we have about 70% reach. That means the average OTS is 300 / 70 = 4.2.
How many TVRs do you need?
To calculate this you need to multiply your target reach by your required OTS. So if you wanted 70% reach at 4 OTS your calculation would be 70 x 4 = 280 TVRs. If you wanted 70% reach at 5 OTS you’d need 350 TVRs. If you wanted 85% reach at 7 OTS you’d need almost 600 TVRs.
Can we calculate reach from TVRs and OTS?
Yes, but only to a point. Reach = TVRs / OTS. So if you are planning 50 TVRs at 1.5 OTS it would seem that your reach would be 30%. However, reach is not easily predictable. This is for two reasons:
- First with you will see that whilst the growth in TVRs is linear, the growth in reach is non-linear i.e. it decreases as you add on every 100 TVRs. Between 0 and 100 TVRs we generate 50% reach. But when we add on the next 100 TVRs we only generate 65% reach at 200 TVRs.
- Different types of campaign on different stations, phased in different ways, with different use of daily schedules (dayparting) will increase reach in different ways. For example, a campaign that runs in weekday daytime between 9am and 5pm may struggle to get over 50% reach even at more than 300 TVRs. This is because you will not be reaching the audience that is working during the day.