It's the first question every business asks when setting up a stamp card, and most get it wrong by guessing: how many stamps should a loyalty card have? Pick too many and customers give up before the first reward — the card sits at three stamps forever and quietly teaches them your program isn't worth the effort. Pick too few and you're giving away margin to people who would have come anyway. The good news is you don't have to guess. There's real research on what makes people finish a stamp card, and the math is simple enough to set up in an afternoon.
How Many Stamps Should a Loyalty Card Have? Start With Visit Frequency
The number on the card matters far less than the time it takes a normal customer to fill it. The rule of thumb: your best regulars should reach the first reward in four to eight weeks. Any longer and the goal feels imaginary; any shorter and you're discounting a habit that already exists.
Work backwards from how often people actually visit:
Daily-to-weekly businesses — 8 to 10 stamps. A coffee shop, juice bar, or karak cafeteria sees its regulars three to five times a week. Ten stamps is two or three weeks of normal behaviour — close enough to feel real, long enough that the free cup rewards genuine loyalty.
Weekly-to-fortnightly businesses — 5 or 6 stamps. A car wash, laundry, or lunch spot that sees customers once a week should land the reward inside six weeks. Ten stamps here means two and a half months of perfect attendance — most customers will do the maths and pass.
Monthly businesses — 4 or 5 stamps. A barbershop, nail salon, or pet groomer runs on a three-to-five-week cycle. Five stamps is already four months of loyalty. Anything more belongs in a points program, not a stamp card.
The Car Wash Experiment Every Business Should Know
In one of the most cited loyalty studies ever run, two researchers handed out stamp cards at a car wash. Half the customers got an 8-stamp card, blank. The other half got a 10-stamp card with two stamps already filled in. Read that again: both groups needed exactly eight washes to earn the free one. Identical effort, identical reward.
The blank 8-stamp cards were completed by 19% of customers. The 10-stamp cards with a head start? 34% — nearly double. And the head-start group finished faster, too.
This is the endowed progress effect: a goal you've already started feels worth finishing, while a goal at zero feels like a decision you haven't made yet. The practical move is almost embarrassingly easy — give every new member their first stamp (or two) the moment they join. "You're already two of the way there" beats "collect ten stamps" every single time, at zero extra cost to you.
Customers Speed Up Near the Finish Line — If They Can See It
A related finding from a café loyalty study: people buy faster the closer they get to the reward. The gap between visits shrinks as the card fills — stamp seven comes quicker than stamp three. Researchers call it the goal-gradient effect; you'll recognise it as the customer who suddenly starts coming in twice a week because "I'm nearly at my free one."
But there's a catch: the effect only works when progress is visible. A paper card buried in a drawer accelerates nothing. This is where a digital punch card quietly outperforms print — the card lives in Apple Wallet or Google Wallet, opens with the phone, and shows seven-out-of-ten every time the customer glances at it. Add a free lock-screen message — "you're two stamps from a free wash" — and you're placing the goal in front of them at exactly the moment the next visit gets decided.
What Should the Reward Be Worth?
A simple benchmark: the reward should be worth roughly 10% of what the customer spends to earn it. Ten coffees at 20 dirhams buys a free coffee — that's 10%, and it works. A free scoop after ten scoops, a free wash after six washes, 25% off the sixth haircut: all in the same zone.
Two more rules. Make the reward your actual product, not a leftover — "a free anything from the menu" beats "a free small drink with conditions" because customers can picture it. And never make the reward feel like fine print: a card people finish and redeem is a marketing asset; a card people finish and get argued with at the till is a story they tell their friends.
Why Paper Cards Break the Math
Here's the uncomfortable part: none of this psychology survives a lost card. Industry estimates suggest most paper stamp cards are lost or forgotten before completion — every one of them a customer who was part-way to a goal and had their progress deleted. The endowed progress effect works in reverse, too: losing a half-full card doesn't just lose the stamps, it makes starting over feel pointless.
A wallet-based stamp card fixes the mechanics without changing the idea. Customers join in one scan of a QR code at the counter — no app, no form — and the card can't be lost, washed, or left in the other bag. You choose the stamp count, pre-fill the head start automatically for every new joiner, and watch actual completion rates instead of guessing. Businesses running digital stamp cards with Wally typically go live the same day, one printed QR code and all.
The Short Version
Match the stamp count to visit frequency (8–10 for daily habits, 5–6 for weekly, 4–5 for monthly). Give a head start — it nearly doubled completion in the car wash study. Keep progress visible so the goal-gradient effect can do its work. Make the reward about 10% back, in your best product. And put the card somewhere it can't be lost.
Ready to set yours up? Book a quick demo with Wally — stamp cards in Apple Wallet and Google Wallet with head-start stamps, visible progress, and free lock-screen nudges, live before your next rush.