Story of a Side Project, Part 1

(This is the first of a handful of posts about my 2015 side project, CamelCalculators.com. This was a site I built and operated to rent TI-84 graphing calculators to college students.)

If you’ve taken a math class this century, you probably recognize the TI-84 Plus Graphing Calculator (or its predecessor, the TI-83). These underpowered, overpriced technological dinosaurs have dominated math classrooms for years.

Last January, I was cleaning out my desk and came across my own TI-84 Plus. I bought it in 2006, and it’s helped me through 2 years of calculus in high school and 4 years of math in college. There are many like it, but this one is mine.

Since it wasn’t doing me any good sitting in a drawer, I checked Amazon to see if it was worth anything. A lot has changed in the past 10 years, so I wasn’t expecting much.

I was shocked.

Not only was the TI-84 Plus still in use, it’s still the #1 most popular calculator on Amazon. And it costs just as much as it did when I bought mine: $100–120.

Keep in mind, most students purchasing graphing calculators will only use them for 1 or 2 required math classes. It’s a significant purchase.

As I was looking at my TI-84, the wheels started turning, and I wondered if I could set up a little rental business for graphing calculators, starting with my inventory of 1. Time to put this purchase back to use.

Lessons learned from renting textbooks

I wasn’t going into this experiment blind. I spent 4 years as a product manager at Chegg, the leading textbook rental site for college students. Although I worked in a different part of the business, I became familiar with the key problems textbook rental faced.

  1. “New” editions are constantly released—Publishers often release new editions of textbooks that contain only minor edits, such as rearranged chapters or new quiz questions. When this happens, the value of the current edition declines to almost zero. Since professors choose the textbooks, students must get the new, more expensive edition. And in an instant, the value of Chegg’s inventory plummets.
  2. Inventory condition deteriorates quickly — Although most can appreciate the smell of an old book, they’d rather not have the torn pages, creased corners, and broken spines that come along with it. But this wear and tear is inevitable, no matter how careful a student is. Chegg had to retire and replace books in its inventory every couple years.
  3. Shipping is costly and difficult — Students who rent textbooks are concerned with saving money. And in the age of Amazon Prime, charging for shipping seems like a rip-off. But when you’re a small startup shipping big, heavy books, free shipping is a tough pill to swallow. Roundtrip shipping costs could be upwards of $25 on an $80 order.

Textbook rental is a tough business, which is why Chegg has since branched out into more profitable online student services like homework help, test prep, and tutoring.

Evaluating the calculator business

Remembering these problems from my days at Chegg, I was curious to see how a calculator rental business might be different.

  1. “New” editions are never released — Technology has improved tremendously since 2004, but graphing calculators have remained the same. The reason? Teachers. When teachers introduce graphing calculators in their classes, they have to teach students how to use them. And that process is much easier when everyone has the same calculator. Teachers across the country tell their students, “Get a TI-83 or TI-84.”
  2. Inventory condition rarely deteriorates — While books get damaged fairly easily, a graphing calculator is built like a tank. It’s made of tough black plastic that hides scratches, has a protective slide case, and can handle everyday use just fine. I used my calculator for a solid 6 years, and it would still pass for “Like New” condition.
  3. Shipping is easy and cheap — My TI-84, when wrapped in bubble wrap, fit perfectly inside a USPS small flat rate box. I could then ship that box anywhere in the USA in 2–3 days for just $5.

I began to realize I was onto something. Calculator rental avoided most of the problems of textbook rental. There was little risk of my inventory becoming obsolete unless the math teachers of America suddenly changed their recommendations. Calculators were unlikely to be damaged in transit or through use. And the shipping costs were a consistent, manageable $5.

I was ready to give it a go.


In part 2, I’ll explain how I tested this idea in a weekend and rented my first calculator. All without writing a line of code.

Update: Part 2 is here

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