Free · private · in your browser
Debt calculators that show their working
Thirteen calculators for paying off debt, credit cards, consolidation, loans, credit health and UK student loans. Free, private, and worked out on your device with every step shown.
Worked example · avalanche payoff
£5,000.00 at 24% and £10,000.00 at 6%, paying £600.00 a month
- Credit cardcleared month 13
- Personal loancleared month 28
interest = balance × APR ÷ 12, highest APR first
Debt-free in 28 months£1,662.26 interest
Try it with your debts- Formulas checked against official guidance
- Calculated in your browser
- Every assumption shown and explained
What do you want to work out?
Every calculator updates as you type, shows each step of the maths, and exports to CSV. Pick a currency once and it’s remembered on this device.
Pay off debt
Work out the fastest or cheapest way to clear what you owe, month by month.
Credit cards
What a card balance really costs, and the fastest way to clear it.
Consolidate
See whether one new loan or a balance transfer beats keeping your debts separate.
Loans
Pay an existing loan off early and see what it saves.
Credit health
The ratios lenders and credit bureaus look at, worked out from your own figures.
Student loans
What you repay each month and whether the loan is ever cleared.
Numbers you can check, not just numbers
Most debt calculators give you a total and ask you to trust it. DebtWren shows the working instead. Open Show working under any result and you’ll see each step: the interest charged each month, the payment applied to each debt, and the rounding used. If a figure looks surprising, you can follow it back to where it came from.
The same calculators work in any currency. Choose your currency and the amounts format the way you write them. Interest is charged monthly at APR ÷ 12 — the convention most cards and loans use — and every result says which convention it applied.
Everything happens in your browser. The balances, rates and payments you type are not sent to our servers, there’s nothing to sign up for, and nothing is saved unless you choose to keep it. Share links carry your figures in the part of the address after the #, which browsers don’t send to websites.
We calculate and explain; we never advise. You won’t find product recommendations or “you should” here. Where a decision depends on things we can’t see — your lender’s exact minimum-payment rules, fees or promotional rates — the calculator says so.
Show working
Every result lists its steps, formula and rounding, generated by the same code that produced the figure.
Any currency
ISO currency rules, so yen have no decimals and dinars have three. Amounts up to a trillion stay exact.
Free exports
Copy a summary, download the full schedule as CSV, print a clean page or share a link. No paywall.
Private by design
No accounts and no uploads. Nothing you type is sent to us or stored.
What changed, and when
- Calculators
Ten new calculators: credit card payoff, credit card interest, debt snowball, debt avalanche, balance transfer, loan payoff, car loan payoff (with bi-weekly and settlement estimates), debt-to-income ratio, credit utilization and UK student loan repayment. Each is documented on the methodology page and tested against engine-computed worked examples.
- Calculators
First release of the debt calculators: avalanche vs snowball payoff, credit card minimum payments and debt consolidation. Each is tested against the worked examples in our specification.
Understand the maths
- Debt avalanche vs debt snowball: how each method works and what it costsHighest rate first or smallest balance first, worked through month by month.
- Credit card minimum payments explained: the slow way out of debtHow minimums are set, why they barely dent the balance, and the real cost of paying only the minimum.
- Debt consolidation loans explained: when one loan beats manyHow consolidating works, what it can save, and the fees and habits that decide if it pays off.
- How credit card interest works: APR, daily interest and grace periodsThe maths behind your card balance, and why the advertised rate is rarely the whole story.
- Debt-to-income ratio explained: the number lenders look atHow DTI is worked out, what counts as income and debt, and what a good ratio looks like.
About DebtWren
DebtWren is run by Infinity Square Labs Ltd, a small UK company that builds free, privacy-first web tools. Read more about us.
Are DebtWren’s calculators really free?
Yes. Every calculator is free to use with no sign-up and no paywall on any result or export. The site is funded by a small number of clearly labelled ads that never appear inside a calculator.
Which debt should I pay off first?
The avalanche method (highest APR first) usually saves the most interest; the snowball method (smallest balance first) clears individual debts sooner, which some people find motivating. DebtWren shows both side by side so you can compare the total interest and time for each.
Is the money I type sent anywhere?
No. Calculations run in your browser. The balances, rates and payments you type are not sent to our servers or stored.
Is this financial advice?
No. DebtWren calculates and explains; it never advises. Results are estimates for general information. Each one shows its working and assumptions, and the disclaimer explains the limits.