Miles per dollar (mpd) tells you how many miles you can earn for every $1 of eligible credit-card spending.
It is one of the most important numbers to understand when comparing miles cards.
But the headline mpd rate does not tell the whole story.
A card advertising 4 mpd may only award that rate for certain transactions, up to a monthly cap, while another card may award 1.2 mpd across a much wider range of eligible spending.
The best mpd is not simply the highest number. It is the highest rate you can reliably earn on spending you were already going to make.
Last updated: 9 September 2026. Card earn rates, caps, exclusions and Merchant Category Codes can change. Always check the latest card terms.
The Basic mpd Formula
The calculation is:
Miles Earned = Eligible Spend × Miles Per Dollar
For example:
| Spend | Earn Rate | Miles Earned |
|---|---|---|
| $100 | 1.2 mpd | 120 |
| $100 | 2.2 mpd | 220 |
| $100 | 4 mpd | 400 |
| $500 | 1.2 mpd | 600 |
| $500 | 4 mpd | 2,000 |
| $1,000 | 4 mpd | 4,000 |
At first glance, the obvious choice appears to be 4 mpd.
The problem is that you only receive 4 mpd if the transaction qualifies.
Base Rate vs Bonus Rate
Many rewards cards effectively have two layers:
Base rewards
Bonus rewards for qualifying transactions
=
Advertised bonus earn rate
Using UOB Preferred Visa as a current example, eligible selected-online and mobile-contactless transactions can earn up to:
UNI$10 per $5 spend = 4 mpd
UOB describes this as a combination of base and bonus UNI$.
If your spending does not qualify for the bonus, you should not assume it will still earn 4 mpd.
Why Bonus Caps Matter
High-mpd cards often limit how much bonus spending qualifies each month.
For UOB Preferred Visa, from October 2025 onward, the bonus UNI$ cap is separated into:
| Bonus Category | Approx. Qualifying Spend Before Bonus Cap |
|---|---|
| Selected Online Transactions | $600 per calendar month |
| Mobile Contactless Transactions | $600 per calendar month |
| Combined Potential | $1,200 per calendar month |
This is based on the current bonus-UNI$ caps and the card’s 10X UNI$ earn structure.
So if you spend:
$600 online + $600 mobile contactless
and all transactions qualify, you can potentially earn the 4 mpd rate across both categories.
Spending beyond the bonus cap should not automatically be treated as another 4 mpd transaction.
Always track your bonus cap. A 4 mpd card can quickly become a much lower-earning card after the bonus limit is reached.
What Is an MCC?
MCC stands for Merchant Category Code.
Card networks assign merchants a code based on the type of business they operate.
Examples could include categories such as:
- Restaurants
- Airlines
- Hotels
- Retail stores
- Government services
- Financial institutions
Banks use these codes when deciding whether a transaction qualifies for rewards or bonus rewards.
This means two transactions that feel similar to you may be treated differently by the bank.
For example, buying something through an app does not automatically mean the transaction qualifies as an eligible “online retail” purchase.
The merchant’s classification still matters.
Why Some Transactions Earn Fewer or No Miles
Every bank maintains its own list of excluded or restricted transactions.
Your original BAM miles strategy specifically highlighted the importance of checking excluded MCCs rather than assuming every online or mobile-wallet transaction earns the headline rate.
Common categories that banks may restrict can include things such as:
- Money transfers
- Financial institutions
- Stored-value top-ups
- Government services
- Certain bill payments or payment-service transactions
The exact list depends on the bank and card.
Do not memorise one old MCC list forever. Check the current card terms because banks can revise exclusions.
Online Spend Does Not Always Mean Bonus Spend
A transaction can happen online but still fail to qualify for a card’s online-spend bonus.
The safest approach is to check:
- Is the merchant eligible?
- Is the transaction processed as an eligible online transaction?
- Is the MCC excluded?
- Have you already reached the monthly bonus cap?
- Does the payment method meet the card’s rules?
If you are uncertain about a large transaction, your original strategy of making a small test purchase first can be useful.
For UOB, Rewards+ in the UOB TMRW app can help you inspect rewards earned on transactions.
Mobile Contactless Spend
Some cards reward mobile contactless spending differently from simply tapping the physical card.
For example, UOB Preferred Visa currently offers its bonus earn rate on qualifying mobile-contactless transactions.
That means the payment method itself can matter.
A useful habit is to know whether the card requires:
- Physical contactless
- Mobile-wallet contactless
- Online payment
- A specific merchant category
before paying.
Points May Be Awarded in Blocks
Another detail beginners often miss is that banks may award rewards using fixed spending blocks.
For example, UOB expresses Preferred Visa rewards as:
UNI$10 per $5 eligible spend
rather than literally awarding four airline miles after every individual dollar.
On small transactions, rounding or award-block rules can therefore affect the exact number of points earned.
For everyday use, 4 mpd is still a useful headline rate, but do not assume the calculation is always perfectly continuous down to every cent.
Overseas mpd Can Be Misleading
Suppose one card gives you:
2.2 mpd overseas
while another payment method gives no miles but has lower foreign-exchange costs.
The miles card is not automatically better.
Citi currently states that foreign-currency card transactions may attract an administrative fee of up to 3.25% on the converted Singapore-dollar amount.
So you should compare:
| Question | Why It Matters |
|---|---|
| How many extra miles am I earning? | Measures the rewards benefit |
| What FX fee am I paying? | Measures the additional cost |
| What value do I realistically get from those miles? | Determines whether the trade-off is worthwhile |
This is why your original strategy used a low-FX payment method for some small overseas purchases rather than blindly chasing miles on every foreign-currency transaction.
A Practical Card-Selection Order
For each purchase, I like to think about the decision in this order:
1. Can I earn 4 mpd or another strong bonus rate?
↓
2. Is the merchant and payment method eligible?
↓
3. Am I still below the monthly bonus cap?
↓
4. If not, what is my best general-spend fallback card?
↓
5. If overseas, are the extra miles worth the FX cost?
This is much more useful than simply asking:
“Which card has the highest mpd?”
Example: A $1,500 Month
Assume you have:
- $500 eligible selected-online spend
- $500 eligible mobile-contactless spend
- $500 other local spend
If the first $1,000 qualifies for a 4 mpd card:
$1,000 × 4 mpd = 4,000 miles
If the remaining $500 goes onto a 1.2 mpd general-spend card:
$500 × 1.2 mpd = 600 miles
Total:
4,600 miles
If you had put the entire $1,500 on a 1.2 mpd card:
$1,500 × 1.2 mpd = 1,800 miles
That is a difference of:
2,800 additional miles
without increasing your spending.
That is the purpose of optimising mpd.
Common mpd Mistakes
Chasing Miles by Spending More
Extra spending defeats the purpose.
The best miles are earned on purchases you would have made anyway.
Forgetting the Monthly Cap
A 4 mpd rate is irrelevant after you have exhausted the eligible bonus allowance.
Assuming Apple Pay or Google Pay Always Qualifies
Eligibility depends on the specific card’s rules.
Ignoring Excluded MCCs
The way the merchant is classified can determine whether bonus rewards are earned.
Ignoring Foreign-Currency Fees
A higher overseas mpd rate is not automatically better after fees.
Looking Only at the Headline Rate
Transfer fees, expiry, annual fees and ease of use also matter.
Key Takeaways
- mpd means miles earned per dollar of eligible spend.
- A high advertised mpd normally comes with conditions.
- Bonus caps determine how much spending can actually earn the headline rate.
- Merchant Category Codes can affect whether a transaction qualifies.
- Payment method can matter — online, mobile wallet and physical-card transactions may be treated differently.
- Overseas mpd should be considered together with foreign-currency fees.
- The goal is to maximise rewards on existing spending, not to spend more.
If you are completely new to miles, start with Miles Basics: How Credit Card Miles Work.
Then see how I put these ideas together in Best Miles Credit Cards for a Simple Setup.
Official Sources
- UOB — Preferred Visa Card
- UOB — Preferred Visa Terms and Conditions
- UOB — Rewards+ and UNI$
- Citi — Fees and Rates
This article is for educational purposes only. Credit-card rewards terms can change and should be checked before making spending decisions.