The Savings vs Debt Maths Nobody Shows You (UK)
By Hamid Ali, MSc Accounting & Finance, ACCA in progress, Founder of DebtShift | Updated July 2026
Run this calculation on your own numbers
The Savings vs Debt Calculator shows you the exact annual pound cost of keeping savings while carrying debt — based on your actual interest rates and balances.
Try the Savings vs Debt Calculator →Nobody sits you down and shows you this table. Your bank doesn’t send it. Your statements don’t calculate it. Even most financial advice glosses over it with “pay off high-interest debt first” — without ever showing you what that actually means in pounds per year.
So here it is. The actual maths. Run it on current UK rates. See what keeping savings while carrying credit card debt is really costing you.
The Maths, Shown Plainly
UK average credit card interest rate: 27.07% (May 2026, Finder/Bank of England data).
Best easy-access savings rate: 5% AER (Revolut/ClearBank, June 2026).
Average easy-access savings rate: 2.49% (Moneyfacts, May 2026).
Here’s what keeping savings alongside credit card debt actually costs per year at different balance levels:
| Balance held in both | Card costs you/yr | Best savings earns/yr | Net annual loss |
|---|---|---|---|
| £500 | £135 | £25 | £110/yr |
| £1,000 | £271 | £50 | £221/yr |
| £2,500 | £677 | £125 | £552/yr |
| £5,000 | £1,354 | £250 | £1,104/yr |
| £8,000 | £2,166 | £400 | £1,766/yr |
| £10,000 | £2,707 | £500 | £2,207/yr |
Based on 27.07% avg credit card rate vs 5% best easy-access rate (June 2026). Simplified annual calculation — actual compound interest will vary.
If you’re at the average easy-access savings rate of 2.49% instead of the best rate, the losses above are even larger. At £5,000 in both: card costs £1,354, average savings earns £125. Net loss: £1,229 a year.
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Run My Numbers →Why the Gap Is So Large in the UK Right Now
The Bank of England base rate is 3.75% as of June 2026. Savings providers pass this on — slowly and partially. The best easy-access accounts now pay around 5%. But credit card lenders have always charged far above base rate because the debt is unsecured. They take the risk of you not paying back, so they charge accordingly.
That structural gap — base rate to savings rate to credit card rate — has always existed. What’s different now is the absolute size. When base rate was 0.1% in 2021, the gap between a 0.5% savings account and a 20% credit card was obvious. Now with a 3.75% base rate, savers feel like they’re finally getting rewarded. They are — but 5% still loses to 27% by 22 percentage points.
The feeling of earning interest on savings is real. The maths still says clear the card first.
The Maths Changes With Different Debt Types
Not all debt creates the same gap. Here’s how the calculation shifts across common UK debt types:
| Debt type | Typical rate | Best savings | Gap | Decision |
|---|---|---|---|---|
| Store card | 30–40% | 5% | 25–35% | Pay first |
| Credit card | 20–35% | 5% | 15–30% | Pay first |
| Personal loan | 7–15% | 5% | 2–10% | Usually pay |
| Mortgage | 4.2–5.7% | 5% | -0.8% to +0.7% | Run numbers |
| 0% credit card | 0% (promo) | 5% | +5% | Save instead |
| Student loan (Plan 2/5) | RPI-linked | 5% | Varies | Don’t overpay |
Mortgage range reflects average fixed rates (~5.5–5.7%) down to the cheapest available deals at lower loan-to-value (~4.2–4.6%) as of mid-2026 — average mortgage debt now costs slightly more than top savings pay, a shift from recent years when overpaying vs saving was more clearly a toss-up.
The One Time Saving Beats Paying Debt
If your debt rate is below your savings rate — save. Right now that means:
0% credit card deals — if you’re on a genuine 0% promotional period, every pound in a 5% easy-access account is earning you money while the debt is free. Clear it in full before the 0% ends. Set a reminder 60 days before it expires — the revert rate is often 25%+.
Mortgages on very low fixed rates — if you fixed at 1.5–2% in 2020–2021 and haven’t remortgaged, your mortgage costs less than the best easy-access savings rate. In this case, saving genuinely does beat overpaying. These situations are increasingly rare as fixed deals expire and roll onto today’s much higher rates, but some people are still in them.
UK student loans — Plan 2 loans write off 30 years after you first become liable to repay. Plan 5 loans (anyone who started university from August 2023 onward) run for 40 years instead — ten years longer — though Plan 5 also charges a lower interest rate (RPI only, versus Plan 2’s RPI plus up to 3%). Either way, the effective rate you pay depends heavily on your income trajectory, and for most borrowers on either plan, the conventional wisdom from financial economists is clear: don’t overpay UK student loans. Save instead, unless you’re confident you’ll clear the balance in full well before write-off.
Want to see your complete debt payoff timeline?
The AI Debt Payoff Planner shows exactly when each debt clears, how much interest you’ll save by overpaying, and what order to pay everything in.
Map My Debt Payoff →What This Means in Practice
Most personal finance advice tells you to pay high-interest debt first. What it doesn’t do is show you the annual pound figure — the actual cost of not doing it.
Someone with £5,000 in both a credit card and a savings account, earning 5% and paying 27%, is losing over £1,100 a year to that decision. Over three years that’s £3,300 gone. Not to bad luck. To an arithmetic gap they never calculated.
Run the number once. It’s usually enough to change the decision permanently.
Read Next
- Savings & Financial Resilience — Full Pillar Hub
- Should You Save or Pay Off Debt First? UK
- How to Pay Off Debt — Snowball vs Avalanche
Questions People Actually Search
Is it better to have savings or pay off debt UK?
If your debt rate is above your savings rate — pay the debt. For credit card debt at 27% vs savings at 5%, paying the debt is a guaranteed 27% return. Nothing beats that. Keep a small emergency buffer (£500–£1,000), clear the expensive debt, then build your full savings pot.
How much interest am I really paying on my credit card?
Divide your APR by 12 to get your monthly rate. A 27% APR means roughly 2.25% charged monthly on your outstanding balance. On £3,000 that’s £67.50 added in month one alone — before you’ve paid a penny toward the balance. The Minimum Payment Calculator shows your full cost over the life of the debt.
Should I use my ISA to pay off debt?
Depends on the ISA type and your debt rate. If it’s a cash ISA earning 4–5% and you have credit card debt at 20%+, the gap is significant — withdrawing some to clear the card may make sense. If it’s a stocks and shares ISA, check whether the investment is likely to be up, and whether you’ll lose the allowance. It’s not a simple yes or no — model the numbers first.
Why do banks not tell you to pay off debt with savings?
Because banks make money on both sides. They pay you 2–5% on savings and charge you 20–35% on credit card debt. The gap between those two rates is profit. They have no financial incentive to encourage you to use savings to clear debt — doing so collapses the spread they earn from you.
What if I need the savings for something specific?
Factor in the timeline. If the purchase is 12+ months away, clearing the debt now and rebuilding savings is usually still cheaper than carrying the card balance throughout. If the purchase is 2–3 months away, keeping the savings and paying the short-term interest cost may be worth the certainty. Use the calculator to model both scenarios with your actual numbers.
Run the exact calculation on your own numbers
Free. No sign-up. Takes 60 seconds. See your annual pound cost of keeping savings while in debt — then decide.
DebtShift provides financial education and AI-powered tools for informational purposes only. This is not regulated financial advice. We are not regulated by the Financial Conduct Authority and do not provide regulated debt advice. If you are struggling with debt, free confidential help is available from StepChange (0800 138 1111) or MoneyHelper. Hamid Ali holds an MSc in Accounting & Finance and is progressing through ACCA.