The formula
How to calculate consolidation savings
Consolidation replaces several debts with one loan at a single rate. The saving is real only when the comparison holds the term constant — otherwise a lower monthly payment can hide a higher total cost.
This calculator amortises the same balance over the same number of years at both rates, so the difference is genuinely attributable to the rate rather than to stretching the debt out.
Here is what each field means:
- Total balances
- Current average rate (% APR)
- Consolidation loan rate (% APR)
- Consolidation term (years)
The result updates on every keystroke. The URL updates too, which makes the filled-in version easy to bookmark or send to someone else.
The order the fields are filled in makes no difference to the result — the calculator recomputes the whole formula from whatever is currently in every field, not step by step. That means it is safe to adjust one number, watch the result change, and adjust it back, without worrying about resetting anything first.
Why consolidation savings matters
A calculation like this usually gets used at a decision point rather than out of curiosity — comparing two real options, checking a number a lender or adviser has quoted, or working out whether a plan that sounded fine in conversation still holds up once it is written down with actual figures. The maths itself is rarely complicated; what is hard is remembering which figures to use and in what order, which is exactly what a dedicated calculator is for.
This tends to come up when comparing two concrete alternatives — two lenders, two savings products, two ways of structuring the same decision — rather than in the abstract. Run both scenarios through the same calculator with the same assumptions and the comparison becomes fair, because the only thing changing between the two results is the number you are actually trying to test.
This kind of calculation rarely stands entirely alone. A consolidation savings figure usually feeds into a wider decision — how it compares with a competing offer, whether it fits inside a monthly budget, what it does to a longer-term plan — and the value of having it as an exact number rather than a rough guess is that those follow-on comparisons stop being guesswork too. Once one figure in a decision is precise, it is worth making the effort to get the others precise as well, rather than mixing an exact calculation with several estimates and treating the result as equally reliable.
In practice, most people arrive at a page like this one having already tried a version of the calculation by hand or in a spreadsheet, and use the calculator here to confirm it rather than replace it. That is a reasonable way to use it — the two should agree to the last decimal place if the same inputs and the same formula are used, and if they do not, the formula shown above is the one to check your own working against first.
Worked example
Work through the defaults on this page:
- Total balances: 14,000
- Current average rate: 22.5 % APR
- Consolidation loan rate: 9.9 % APR
- Consolidation term: 4 years
That gives:
- Interest saved over the term: 4,343.52
- New monthly payment: 354.4
- Monthly saving: 90.49
These figures are only the calculator's own starting values, included so the working is visible rather than hidden inside the tool above. Replace them with your own numbers and the same arithmetic applies — nothing about the method changes, only the inputs feeding it.
Reading the result
Cutting the rate from 22.5% to 9.9% on £14,000 over four years saves several thousand pounds. That is the honest gain; anything advertised on top of it is usually the effect of a longer term.
Where this goes wrong. Consolidating and then using the cleared cards again. The single most common outcome of consolidation is a consolidation loan plus new card balances a year later.
A useful check on any unfamiliar result is to compare it against a rough mental estimate first — round the inputs to convenient numbers and see whether the calculator's answer lands in roughly the same territory. A wildly different figure usually means one of the fields was entered in the wrong unit, most often a percentage typed as a whole number where a decimal was expected, or the reverse.
A hard search and a new account dip it briefly, then utilisation falls as the cards are cleared, which usually helps within a few months. Missing payments on the new loan is the only serious risk.
It buys a lower rate and converts unsecured debt into debt your house guarantees. Given that a personal loan default damages your credit while a secured default can cost you the property, the rate saving needs to be substantial to justify it.
The answer it gives you is interest saved over the term. With 14,000 total balances, 22.5 % APR current average rate and 9.9 % APR consolidation loan rate, that comes to 4,343.52. Change any field and the figure moves with it.
Whenever one of the underlying figures changes — a new interest rate, a different balance, an updated term — since the result only reflects what is currently in the fields. There is no need to keep a separate record of past results; the web address for a filled-in version already carries the figures used to produce it.
Not unless a tax rate or a fee is explicitly one of the inputs above. Where it is not, the figure shown is a gross calculation, and any tax due depends on your personal circumstances and current tax rules, which are worth checking separately.
The arithmetic itself is exact — the calculator applies the formula shown above precisely, with no rounding until the final figure is displayed. The uncertainty, where it exists, is entirely in the inputs: an estimated rate or an approximate balance carries that same approximation through to the result.