Which card, right now?
Card guides rank cards in general. This answers the question you actually have at the register: for this purchase, with the cards you hold, which one — and is the portal or offer even legal to stack? One answer, in dollars, math shown.
What an answer looks like
A $120 dinner, two-card wallet
You hold a Chase Sapphire Reserve and a Chase Freedom Unlimited, pay in full each month, and the check at a restaurant is $120. Which card?
Pay with Chase Sapphire Reserve — $4.50 back on this $120.00 purchase.
Pay with Chase Sapphire Reserve ($4.50) = $4.50 on $120.00 at a restaurant
| Pay with | Card earn | Offer | Portal | Total back |
|---|---|---|---|---|
| Chase Sapphire Reserve | $4.50 | $0.00 | $0.00 | $4.50 |
| Chase Freedom Unlimited | $3.60 | $0.00 | $0.00 | $3.60 |
This is the form’s starting setup — press “Get the answer” below without changing anything and you’ll get this exact answer.
A $200 gift card through a 4% portal
Same wallet, but now it’s a $200 gift card bought through a shopping portal advertising 4% back. Most guides would count the portal; the engine knows portals routinely exclude gift-card purchases and prices that layer at $0.
Pay with Chase Freedom Unlimited — $3.00 back on this $200.00 purchase.
Pay with Chase Freedom Unlimited ($3.00) = $3.00 on $200.00 at an electronics store
- Not counted: a shopping portal's 4% portal rate is not counted: portals commonly exclude gift-card purchases from earning.
| Pay with | Card earn | Offer | Portal | Total back |
|---|---|---|---|---|
| Chase Freedom Unlimited | $3.00 | $0.00 | $0.00 | $3.00 |
| Chase Sapphire Reserve | $2.50 | $0.00 | $0.00 | $2.50 |
To reproduce it below: category “Everything else”, amount 200, tick the gift-card box, portal rate 4.
Computed 2026-07-28 from the issuer-verified facts catalog v0.6.1 (28 cards) at conservative floor point values (why floors), by the same engine the form below calls (@pointsbrain/engine@0.0.1, snapshot catalog-e9463e48). Not financial advice.
The stacking rules, enforced — not just described
A rewards stack (card × portal × card-linked offer) does not compose freely; the layers conflict in ways most guides gloss over. These rules run inside the engine on every answer above:
- card-linked offer × paying card: A card-linked offer (Chase Offer, Amex Offer…) earns only when you pay with the exact card it is attached to.
- gift-card purchase × shopping portal: Shopping portals commonly exclude gift-card purchases from cash back, so portal earnings are counted at $0 on a gift-card purchase.
- gift-card purchase × card-linked offer: Card-linked offers commonly exclude gift-card purchases, so offer earnings are counted at $0 on a gift-card purchase.
- hotel stay × bank travel portal: Hotel stays booked through a bank travel portal usually forfeit elite night credit, promotions, and upgrades; flights generally credit fine.
If you carry a balance month to month, the engine refuses to answer and says why: at typical card APRs, interest costs more than any rewards rate returns. Paying in full comes first.
For software and agents
This page and the API are the same computation (@pointsbrain/engine@0.0.1). GET /api/answer returns the contract; POST /api/answer resolves a spend moment against a declared wallet and echoes X-Engine-Version and X-Snapshot-Version on every response, so any answer can be reproduced against the exact facts it was computed from. If the facts catalog fails its freshness validation, the API refuses rather than serving stale numbers. Educational software, not financial advice; affiliate payouts carry zero weight, always.