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Increase Sales by Displaying an Incentive Calculator on Your Sales Page

By William Bontrager

Does your sales page print cost/profit ratios or other numbers to show prospective customer how much they could gain from purchase of your product or service?

Might your sales improve from publishing such numbers?

This article reveals a method that may be many times more effective than the mere publishing of numbers. It's a calculator allowing prospective customers to estimate number of sales and/or other factors. They then click a button for the total profit or other benefits calculated from their own estimates, which can be sufficient incentive to buy.

Allow prospects to sell themselves.

Yes, publish tables and formulas with representative or example numbers. But also provide the calculator to let prospective customers see results using their own estimates based on their perception of their own potential or ability.

Those with greed or gambling tendencies may overestimate their ability to perform, and the resulting calculations can sell them. Those who understand their own abilities may estimate closer to their actual potential, and the resulting calculations can convince them of the viability of your offer -- provided your product/service has actual profit potential, of course.

The example and the working JavaScript calculator used in this article are for a new professional book "print on demand" (POD) service offered by a client and friend of ours. The example calculator on the demo page, where you can also obtain the source code, is at

If you have a book you want to print and sell, know that the numbers in the example calculator are real. It can be convincing, even without knowing anything about the printed books' quality, their binding, or anything else about the service.

(I can't guarantee the prices won't change, of course, because the POD service isn't our own. To those who might read this in the future, the prices were correct when the article was first published and the JavaScript first developed.)

The following is a section describing how the incentive calculator works, using as example a calculator created for a real-world web site, a POD service. A few other examples of use that the incentive calculator might be customized for are listed below the tutorial section. You'll think of more uses.

The description of how it works is designed to provide information sufficient for a moderately-skilled JavaScript programmer to modify the calculator to meet other sites' requirements.

How It Works

The example incentive calculator, along with links to download the complete source code, is at

The JavaScript code may be either in the HEAD area of the page or in the BODY area of the page above the form.

The Form --

You'll notice that the form has three fields for the prospective customer to enter data into, a set of radio buttons, and three fields within which to print calculation results.

In order to do the calculation, the form needs a name. In the example, we use name="incentivecalc"

The three fields for the prospective customer to enter data into are:

     1. name="pages"
The number of book pages is entered here. This is a "print on demand" service and part of the book cost is based on the number of pages.
2. name="retail" The retail price of the book. 3. name="copies" The number of books the prospective customer estimates will be sold.

From those three items, the value of the three results fields can be calculated:

     1. name="sales"
        This field will contain the total sales, retail
        multiplied by copies.

     2. name="cost"
        This will contain the total cost, the cost of
        one book (calculated using the number of pages)
        multiplied by copies.

     3. name="profit"
        The profit field contains the result of subtracting
        cost from sales.

In the source code, notice the READONLY attribute in the input tags for the three fields that contain the calculated results. Most browsers will not allow a user to type information into form fields with that attribute. But JavaScript can change the field's value.

The radio buttons in the form demonstrate versatility that may be built into an incentive calculator.

The top button causes the cost of each book to be the actual printing charge.

The bottom button causes the cost of each book to be the printing charge plus cost of order fulfillment, which includes everything that needs to be done to print the book and deliver it to the customer.

The form button has an onClick="CalculateProfit();" attribute. When this button is clicked, calculation occurs.

The JavaScript and Building Your Own --

Detailed descriptions of the JavaScript code and a couple paragraphs on how to go about building your own incentive calculator are embedded as an HTML comment in the source code.

Other Examples of Use

The calculator can be customized to:

     ~~ Calculate the number of extra visitors at the end
        of a certain time period if __% recommend the site
        and __% of those recommended then also recommend
        the site to their own friends. Let the user type
        in the current number of visitors per day and the
        two percentages.

     ~~ Calculate example monthly check amounts for
        two-level affiliate commissions. Let the user
        type in the number of personal sales, the number
        of second-level affiliates, and the average number
        of sales by those affiliates.

     ~~ Let the user type in the number of miles s/he
        drives in a given year, the price of gas/petrol,
        and the consumption rate per mile/kilometer to
        calculate an estimate of the total savings after
        installing your mechanical fuel saver device. A
        display of before and after fuel cost might provide
        additional incentive.

Those are just a few examples. Your own business may suggest ways you could use the idea.

Will Bontrager

About the Author:

William Bontrager Programmer/Publisher, "WillMaster Possibilities" ezine

Are you looking for top quality scripts? Visit Willmaster and check out his highly acclaimed Master Series scripts. Some free, some for a fee.