Gibson Njine spent about nineteen months building software to solve a problem most people just put up with: when a group eats together the bill gets split evenly, and whoever ordered least ends up paying for whoever ordered most.
He co-founded Celipa in late 2021, in his second year at Babson College in Massachusetts, with two classmates, Mpho Montsho and Emory Clark. One diner photographed the receipt. The others joined the same digital copy by scanning a QR code, tapped what they had ordered, and the app worked out what each of them owed.
“We used Amazon’s document service to read the receipt. That part’s a solved problem and I wouldn’t claim otherwise,” Njine says. “The difficulty is what comes after. You’ve got a list of items and a printed total and four people on four phones all claiming things at once. Two of them tap the same plate of fries within about a second of each other. And then, well — somebody has to decide what the app does about that. There isn’t an obvious answer.”
Celipa handled it with a real-time layer that kept the shared receipt consistent across every device viewing it, so a claim made on one phone showed up immediately on the others. Njine built it across the first half of 2022.
Splitting it properly
Most bill-splitting software divides tax and tip by headcount. Celipa divided them in proportion to what each person had claimed. If your food came to fifteen per cent of the bill, you paid fifteen per cent of the tax.
“It’s more work, which is probably why nobody does it,” Njine says. “You have to work out each person’s share of the subtotal before you can do anything else. But splitting the tax evenly is just wrong. It changes the answer for basically any table where people ordered different things.”
He shipped that in November 2022. Earlier the same year he had added quantity-aware claiming, so a line item covering three of something divided by units taken rather than by heads.
Njine worked on the backend, the administrative dashboard and the mobile app.
Apple approved Celipa for the App Store on 29 September 2022. Apple’s analytics record 617 first-time downloads. The conversion rate, the share of people who looked at the product page and went on to install it, averaged 54.67 per cent. The App Store median sits somewhere between two and five per cent.
Testing it on students
The team’s first focus group was scheduled for early March 2023 and cancelled that morning because of snow. The rescheduled session was set for Friday 24 March, 2:30pm, in Horn Commons 101. Attendees were asked to bring two to four friends so the team could hear from people who hadn’t used the app, and were told an iPhone was required. There would be snacks.
What came out of those sessions, Njine says, wasn’t really about the technology.
“People would say it’s easy, and then when you pushed them it turned out easy wasn’t the point. Splitting a bill is awkward and everyone pretends it isn’t. Somebody has to be the one who says, actually, I only had the soup, and nobody wants to be that person. So the table splits it evenly and a couple of people quietly pay for everyone else’s drinks.”
“What the app did was take that conversation away. You tap what you had, the math happens, nobody has to say anything out loud. I think that’s what people actually liked. I’m not sure most of them noticed the receipt scanning.”
Celipa was funded by Babson College’s Butler Launch Pad, part of the Arthur M. Blank Center for Entrepreneurship, which selected it for its seed fund in two consecutive cycles in 2022. It also received cloud credits through the college’s Launchpad programme.
Zhi Li, who teaches software development at Babson, taught Njine in his Web Technologies course in the autumn of 2022. Celipa was not a course assignment and Li had no hand in it, but he questioned Njine about the system’s architecture at length.
Li has written that Njine could answer at whatever level of the architecture he chose, from the data model down to individual edge cases, without deferring to a collaborator, which in his experience is the most reliable indication of authorship an instructor has. Li has taught more than a thousand students in twelve years.
Njine graduated magna cum laude in December 2023. He now works as a software engineer at Microsoft in Redmond, Washington, on back-end platform and cloud infrastructure.
