How To Forecast The Success Of Your Direct Mail Campaign Using a Doubling Day

Thinking about doing a direct mail campaign? You might be asking yourself how you might be able to forecast the overall success rate of your campaign without waiting months for the mailing’s life cycle to end.

Direct marketers have a nifty trick up their sleeves called a doubling day that solves just that problem. A doubling day is the point in the life cycle of a direct mail campaign where approximately half of all the responses that the mailing will generate will have arrived. As a general rule, a doubling day is within two weeks of the first response.

Why is a Doubling Day Important?

The complete life cycle for a direct mail campaign can take many months to run its course. Certainly, non-profit organizations know that it’s not uncommon for business-reply responses on a mailer to trickle in a year after the mailing was sent. Tracking a single campaign for that long is not very effective or practical because direct marketers often need to send out more direct mail campaigns and they need the results from the last mailer to adjust their current mailers to maximize the overall effectiveness of the campaign.

How to calculate a doubling day

  • Launch your campaign. In order for a doubling day estimate to work, all your mail pieces must be sent off at the same time.
  • Watch for the first response. Your doubling day counter starts on the day that you receive your first response from your campaign. Don't make the mistake of starting your counter the day your campaign launches as this won’t generate reliable results.
  • Start tracking the responses that you get for the next 14 days. For the next 2 weeks after your initial response, you’ll want to keep a close count of all the responses that you get from your campaign. Although 14 days is a rough estimate, generally about half of all the responses that you get will come through within that time. Obviously, the more mailings that you do, the more accurate your doubling day will be.
  • Calculate your doubling day. On the 14 day, count the total number of responses that you have received since the first response and then multiply that number by two. That number should give you a fairly accurate prediction on the overall success of your mail campaign.

Postcard Example

So let’s say that I sent a postcard mailer consisting of 5,000 pieces that were mailed on April 1st. Seven days later, on April 7th I received my first response. I then started tracking all the responses that were generated from the postcard mailing for the next two weeks. On April 20th, I counted up all the responses that I’ve received up until that point which came out to be 25. I then multiplied that number by 2 and got 50. So what I can forecast about my postcard campaign is that it will generate a total of 50 responses over the course of its life time - a 1% response rate.

Factors that Can Affect a Doubling Day Estimation

Keep in mind that using a doubling day estimation is not a concrete science and there are a variety of factors that can throw off the approximation. These include:

  • Location where the pieces are mailed to.
  • Class of mail used.
  • Contents of the direct mail package.
  • Time of year.
  • Mailing house that is handling the campaign.


The beauty of forecasting your direct mail campaign using a doubling day is that you have a solid predictor of the overall success or failure of a mailing campaign within a couple of weeks without waiting months for the campaign to run its course. This technique can also be applied to email campaigns, but we'll get into that in another post.

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