A transfer bonus is one of the most effective marketing tools in loyalty. "Transfer your points now and get 25% more." It reads like free money, and sometimes it is. But a bonus is also a lever the program pulls to move your flexible points into a place where they are harder to get back and often worth less. Whether it is a genuine win or a polite trap comes down to one thing: the math on a redemption you would actually book. Here is how to run it.
What a transfer bonus actually does
Start with what is happening underneath the offer. Most transfer bonuses move points from a flexible currency (the kind you can send to many different partners) into one specific airline or hotel program. The bonus boosts the amount that lands on the other side. Transfer 40,000 with a 25% bonus and 50,000 arrive.
Two things matter here. First, the transfer is almost always one way and final. Once those points become airline miles, you cannot turn them back into flexible points, ever. Second, flexible points are worth more precisely because they keep their options open. A bonus asks you to give up that flexibility in exchange for a bigger number. Sometimes the bigger number is worth it. Sometimes you are trading a dollar of optionality for ninety cents of locked-in miles, and the bonus is the bow on top.
When a bonus is genuinely worth acting on
A bonus is a real win under a specific set of conditions, and they need to line up together.
You have a concrete redemption in mind, in that exact program, that you will book soon. The destination program prices that redemption well (good value before the bonus even applies). And the bonus pushes an already-good deal from good to clearly better. When all three are true, transferring is straightforward. You were going to make this redemption anyway, the program was the right home for the points anyway, and the bonus just handed you a discount. Take it.
So the test is not "is 25% a lot?" The test is "do I have a redemption here that already made sense without the bonus?" If yes, the bonus is gravy. If no, keep reading.
When it is a nudge, not a gift
The bonus turns against you the moment it becomes the reason for the transfer. That is the tell. If the only thing making the destination program attractive is the bonus itself, you are being steered.
Watch for these. You do not have a specific trip, you are just transferring "to lock in the bonus." The destination program redeems poorly, so even with extra points you come out behind. Or you are moving points into a currency you rarely use, where they will sit and quietly depreciate while your flexible points would have stayed useful for anything. In each case the bonus is doing exactly its job: moving your value into a place that benefits the program more than it benefits you. A 25% bonus on a redemption that is 30% worse is a loss wearing a discount sticker.
How do you run the math?
Keep it concrete. Pick the actual thing you want to book.
Find what it costs in the destination program. Suppose a flight is 50,000 miles there. With a 25% transfer bonus, you only need to send about 40,000 of your flexible points to cover it (because 40,000 plus the 25% bonus equals 50,000). Now ask the key question: what does the same flight, or an equivalent one, cost if you book it directly with your flexible points or through a different partner? If booking it your existing way costs 45,000 flexible points, then the bonus route at 40,000 genuinely saves you points. Transfer.
But if the same trip costs 38,000 booked another way, the bonus route at 40,000 is worse, even with the headline 25% attached. The bonus made a bad path look like a good one. This is the whole game. You are not comparing the bonus to nothing. You are comparing the bonused redemption to your best alternative for the same trip.
One more rule. Do the math before you transfer, never after. Because after is too late: the points are stranded, and the only thing left to do is talk yourself into the trip.
The short version
A transfer bonus is worth acting on when you already had a good redemption lined up in that program and the bonus sweetens it. It is a trap when the bonus is the only reason the transfer looks smart. The difference is always a specific trip and a side-by-side comparison, not the size of the percentage.
And if you run the numbers and no redemption clears the bar (no trip is worth it, the programs all price poorly, the flexible points are just sitting there), that is useful information too. At that point the honest comparison is not points versus points. It is points versus cash.