Estimated Monthly Payment
£2,572.62
- Principal & Interest
- £2,022.62
- Property Tax
- £400.00
- Insurance
- £150.00
£320,000.00
£80,000.00
£408,142.36
£808,142.36
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| Loan Term | Monthly P&I | Total Interest | Total Cost |
|---|---|---|---|
| 30 years | £2,022.62 | £408,142.36 | £808,142.36 |
| 20 years | £2,385.83 | £252,600.17 | £652,600.17 |
| 15 years | £2,787.54 | £181,757.84 | £581,757.84 |
| 10 years | £3,633.54 | £116,024.23 | £516,024.23 |
| Year | Principal | Interest | Remaining Balance |
|---|---|---|---|
| 1 | £3,576.72 | £20,694.69 | £316,423.28 |
| 2 | £3,816.26 | £20,455.15 | £312,607.02 |
| 3 | £4,071.84 | £20,199.57 | £308,535.17 |
| 4 | £4,344.54 | £19,926.87 | £304,190.63 |
| 5 | £4,635.50 | £19,635.91 | £299,555.13 |
| ... | |||
| 10 | £6,410.06 | £17,861.36 | £271,283.60 |
| ... | |||
| 15 | £8,863.94 | £15,407.48 | £232,189.25 |
| ... | |||
| 20 | £12,257.20 | £12,014.21 | £178,128.90 |
| ... | |||
| 25 | £16,949.47 | £7,321.94 | £103,373.32 |
| ... | |||
| 28 | £20,588.05 | £3,683.37 | £45,404.89 |
| 29 | £21,966.86 | £2,304.55 | £23,438.03 |
| 30 | £23,438.03 | £833.39 | £0.00 |
How this calculator works
One amortisation formula, two flat monthly add-ons and a conditional insurance charge. Here is exactly what the tool above does with your six inputs.
The formula
monthly = M + (P x t / 100) / 12 + S / 12 + U where M = L x i x (1 + i)^n / ((1 + i)^n - 1)- P
- Home price, exactly as typed. Parsed as a decimal; blank or non-numeric is treated as zero.
- d
- Down payment as a percentage of the price. Slider, whole points, 3 to 50, default 20.
- L
- Loan amount = P x (1 - d / 100). The down payment is never entered as a cash figure.
- i
- Monthly interest rate = r / 100 / 12, where r is the annual rate you entered. A plain division by 12, with no effective-annual conversion.
- n
- Number of monthly payments = y x 12, where y is the term in years (30, 20, 15 or 10).
- M
- Monthly principal and interest — the level payment that clears L over exactly n months.
- t
- Annual property tax rate, applied to the purchase price P and not to the loan or to any later valuation.
- S
- Annual home insurance premium, divided by 12 and never uprated.
- U
- PMI = L x 0.007 / 12 when d is below 20, otherwise zero. A flat 0.7% of the original loan, charged for the whole term.
Two special cases short-circuit the formula. When i is zero or the rate field is empty, M becomes L / n rather than dividing by zero. When L or n is zero or negative, M is reported as zero but property tax and insurance are still shown, because they do not depend on the loan. Total interest is M x n - L and total cost is M x n + the down payment, so neither total includes tax, insurance or PMI. Results are rounded to two decimal places only for display.
Six inputs drive everything on screen: purchase price, interest rate, down payment percentage, term, an annual property tax rate and an annual insurance amount. The first four determine the loan and its repayment; the last two are bolted on afterwards and never touch the loan arithmetic at all. Understanding that split explains most of what the results do.
The loan itself is the ordinary level-payment calculation. The down payment slider is a percentage of the price, so the loan amount is the price less that percentage, and the payment is the single fixed monthly amount that clears that balance in exactly the number of months you chose. The tool converts your annual rate to a monthly one by dividing by 12 and nothing more — no effective-annual-rate conversion, no daily interest. That is precisely how a US lender computes a monthly payment, which is why the figure should line up with a US quote on the same rate and term. It is also why you should type a UK product rate rather than the APRC, because the APRC already bakes in fees and annual compounding and will push the payment slightly high.
Two edge cases are handled explicitly rather than left to produce nonsense. If the rate is zero — or if the rate field is momentarily empty while you retype it — the standard formula would divide by zero, so the calculator falls back to the loan amount divided by the number of months. And if the loan amount comes out at zero or below, the principal-and-interest payment is reported as zero while property tax and insurance are still shown, because those costs do not depend on there being a loan.
Property tax is your entered percentage of the purchase price, divided by 12. Insurance is your annual figure divided by 12. Private mortgage insurance appears only when the down payment slider is under 20%, and is charged at a flat 0.7% of the original loan amount a year. All three are added to the headline monthly payment and all three are excluded from the amortisation schedule, from total interest and from total cost. Every displayed figure is computed at full precision and rounded to two decimal places only at the end, except the amortisation rows, which are passed through unrounded and have their closing balance clamped at zero so floating-point drift cannot show you owing a fraction of a cent in year 30.
A worked example
One full run of the arithmetic, in US dollars, on a $440,000 home with 20% down at 6.69% over 30 years.
Suppose you are buying a $440,000 home with 20% down at 6.69% over 30 years
Worked example- Down payment = 440,000 x 0.20
- $88,000
- Loan amount (L) = 440,000 - 88,000
- $352,000
- Monthly rate (i) = 6.69 / 100 / 12
- 0.005575
- Payments (n) = 30 x 12
- 360
- Growth factor = (1.005575)^360
- 7.399602
- P&I (M) = 352,000 x 0.005575 x 7.399602 / 6.399602
- $2,269.04
- Property tax = 440,000 x 0.012 / 12
- $440.00
- Insurance = 1,800 / 12
- $150.00
- PMI = 0, because the deposit is not below 20%
- $0.00
Follow it further. Total of the P&I payments is 2,269.04 x 360 = $816,855.87, so total interest is $464,855.87 — more than the loan itself — and the total cost figure adds the down payment to reach $904,855.87. In the first month, interest is 352,000 x 0.005575 = $1,962.40 and only $306.64 comes off the balance, which is why the early rows of the amortisation schedule look so lopsided. Drop the deposit to 10% and the loan rises to $396,000, PMI switches on at $231.00 a month, and the monthly total jumps to $3,373.67. Switch instead to a 15-year term at the same 6.69% and the payment rises to $3,103.18 while total interest falls to $206,573.07 — and because 15-year money is genuinely cheaper, re-running it at the 6.01% US 15-year average brings the payment down to $2,972.28.
How to read your result
What the monthly figure has to clear, how it compares with current rates and prices, and what to change first.
The monthly total is the number that matters, and it is bigger than the number most people carry in their heads, because it includes the escrow items. On the example above, principal and interest is $2,269.04 but the actual cash leaving the account is $2,859.04 — the tax and insurance add 26% on top. Any affordability judgement you make from the principal-and-interest figure alone will be a quarter too optimistic.
To turn that into a verdict you need your income, which this calculator never asks for. The long-standing US underwriting guideline is that housing costs stay below 28% of gross monthly income and all debt payments below 36%. Run the example backwards: $2,859.04 divided by 0.28 implies gross income of about $10,211 a month, or roughly $122,500 a year, to sit comfortably inside that rule on a home priced at roughly the US median. That is the arithmetic behind the affordability squeeze, and it is why the National Association of Realtors put its Housing Affordability Index at 102.3 in June 2026 — a median-income family had only just enough income to qualify for a median-priced home, though that was an improvement on 95.5 a year earlier.
Rates and prices give the other half of the context. In the US, the 30-year fixed averaged 6.69% in the week ending 6 August 2026 and the median existing home sold for an all-time high of $440,600 in June 2026. In the UK, the average quoted two-year fix at 75% loan-to-value was 4.79% in July 2026 against an average house price of £271,000 in May 2026. Note the asymmetry: UK borrowers pay a lower headline rate but almost never fix for the whole term, and the average lender revert-to rate — the old standard variable rate — sat at 6.60% in July 2026, nearly two points above the new-deal rate. A UK payment from this calculator is a payment for the fixed period only.
Three things to do with your result. First, compare it with what you pay now, including tax and insurance, not just rent against principal and interest. Second, if the number is uncomfortable, change the price before you change the term — a longer term lowers the payment but the total interest column in the comparison table shows what that costs. Third, re-run it with a rate half a point higher than you expect: on the example loan that swing is worth about $118 a month, and it is a far more realistic stress test than the one your lender will apply.
6.69%
US 30-year fixed mortgage rate
Week ending 6 August 2026, barely changed from 6.63% a year earlier. The survey covers conventional, conforming purchase loans with 20% down and excellent credit, so a typical applicant is quoted more than this.
6.01%
US 15-year fixed mortgage rate
Same week, about 0.68 percentage points below the 30-year. The comparison table in the calculator applies one rate to every term, so it understates the saving from a shorter mortgage.
$440,600
US median existing-home sale price, June 2026
An all-time high and the 36th straight month of annual growth. Newly built homes are a separate and currently lower series at $398,300, per Census and HUD — do not mix the two.
Source: National Association of Realtors, Existing-Home Sales
4.79%
UK average quoted two-year fix at 75% LTV, July 2026
The five-year fix was cheaper at 4.61%, reversing the usual order. Quoted rates are weighted monthly averages of the lowest advertised rates at each LTV band, so quote the month rather than calling it the current rate.
Source: Bank of England, quoted household interest rates (IUMBV34)
£271,000
Average UK house price, May 2026
Up 2.7% over the year, provisional. By nation: £292,000 in England, £215,000 in Wales, £196,000 in Scotland, and £198,000 in Northern Ireland in the first quarter of 2026.
What this calculator does not account for
Every simplification in the code, stated plainly, so you know how much weight the number can carry.
PMI never comes off
The tool charges 0.7% of the original loan amount a year for the whole term whenever the down payment slider is below 20%, and it is triggered by that slider alone rather than by your actual equity. Real private mortgage insurance on a conventional US loan can be cancelled at 20% equity and must terminate automatically at 78% of original value, and the rate varies with credit score and loan-to-value rather than being a flat 0.7%. Low-deposit scenarios therefore look worse over a full term than they would be.
Property tax and insurance are frozen at year-one levels
Property tax is a fixed percentage of the price you typed, forever. There is no reassessment, no millage change, no homestead exemption or assessment cap, and no allowance for the fact that insurance premiums have generally risen faster than headline inflation. The monthly total is a year-one estimate, not a level cost for 30 years.
Total interest and total cost exclude everything but the loan
Total interest is the monthly principal-and-interest payment times the number of months, less the loan amount. Total cost is that same run of payments plus the down payment — so it still contains the loan principal, and is not total interest with the deposit added on. Neither figure includes property tax, insurance or PMI, even though all three are in the monthly figure directly above them. Read them as loan figures, not as the cost of owning the home.
The rate is fixed for the entire term
There is no adjustable-rate mortgage, no tracker, and no way to model a UK two- or five-year fix reverting to a lender's standard variable rate at the end of the deal. That matters: the average UK revert-to rate was 6.60% in July 2026 against 4.79% on a new two-year fix, so a payment calculated at the deal rate describes only the first few years.
No fees, points or transaction taxes
Closing costs, origination and arrangement fees, discount points, valuation and legal fees, title insurance, Stamp Duty Land Tax, Land and Buildings Transaction Tax and land transfer taxes are all absent. In England and Northern Ireland alone, standard SDLT starts on the portion above £125,000, and first-time buyer relief disappears entirely above £500,000 — a five-figure cost the calculator knows nothing about.
No overpayments and no early repayment
The schedule assumes the scheduled payment, every month, for the full term. Lump sums, regular overpayments, biweekly payment schedules, offset accounts, redraw facilities, recasting and refinancing are all outside the model — as are early repayment charges. Since overpaying is the biggest lever most borrowers have, treat total interest as an upper bound.
Only four terms, and the comparison table prices them all the same
The dropdown offers 30, 20, 15 and 10 years. There is no 25-year option, which is the standard UK term, and no 40-year option. More importantly, the loan term comparison table applies your single entered rate to all four rows, when shorter mortgages are normally priced lower — 6.01% on a US 15-year against 6.69% on a 30-year in early August 2026. The table understates how much a shorter term really saves.
The down payment is a whole percentage, capped at 50%
The slider moves in whole percentage points between 3% and 50%, so you cannot enter an exact cash deposit, and you cannot model a deposit above half the price. Gifted deposits, shared ownership, Help to Buy style equity loans and second-charge arrangements have no representation at all.
It knows nothing about affordability
No income field, no existing debts, no credit score, no dependants, no stress test. The calculator will happily produce a confident monthly figure for a mortgage no lender would grant you. Affordability is a separate question and needs the debt-to-income calculator alongside this one.
Everything is nominal, and the currency symbol is cosmetic
There is no inflation adjustment anywhere, so a payment in year 30 is shown in the same money as a payment in year one, when in real terms it will be far smaller. The currency symbol is taken from your browser locale or a saved preference and no conversion is applied — enter 400,000 and you get 400,000 of whatever is being displayed.
None of that makes the output useless. The payment arithmetic is exact, and it is the same arithmetic your lender runs. What the calculator gives you is a reliable answer to a narrow question — what does this loan, at this rate, over this term, cost each month — and a deliberately incomplete answer to the wider one about whether you can afford the house. Take the monthly figure into a real budget before you take it to an estate agent.
Frequently asked questions
How is the monthly mortgage payment calculated?
The calculator subtracts your down payment from the purchase price to get the loan amount, converts your annual rate to a monthly rate by dividing by 12, and converts the term to a number of months by multiplying by 12. It then applies the standard level-payment amortisation formula, which produces the one fixed payment that clears the balance exactly at the end of the term. Property tax, insurance and PMI are worked out separately and added on top.
Why is my lender's quote higher than the number here?
Usually because of things this calculator never sees. It has no closing costs, no origination or arrangement fee, no discount points, no HOA or service charge, and no flood or hazard cover beyond the single annual insurance figure you type in. Lenders also price by credit score and loan-to-value, so the rate you are actually offered may be above the headline average you entered.
Does the calculator include PMI, and does the PMI ever stop?
It adds private mortgage insurance whenever the down payment slider sits below 20%, at a flat 0.7% of the original loan amount a year, divided by 12. It never removes it. In reality PMI on a conventional US loan can be cancelled once you reach 20% equity and must be terminated automatically at 78% of the original value, so the calculator overstates the cost of a low deposit over a full term.
Why does the total cost figure look too low?
Because it only counts the loan. Total interest is the monthly principal-and-interest payment multiplied by the number of months, minus the loan amount. Total cost is a separate sum: the same payment multiplied by the number of months, plus your down payment — it is not total interest plus the deposit. Property tax, insurance and PMI appear in the monthly figure but are deliberately left out of both totals, so the real lifetime cost of owning the home is considerably higher than the number shown.
What interest rate should I enter?
The rate on the specific product you are being offered, not an average, if you have one. If you are only estimating, the US 30-year fixed averaged 6.69% in the week ending 6 August 2026 and the 15-year 6.01%, per Freddie Mac's Primary Mortgage Market Survey. Bear in mind that survey covers borrowers with 20% down and excellent credit, so it sits below what a typical applicant is quoted.
Can I use this for a UK mortgage?
For the payment arithmetic, yes: a UK repayment mortgage amortises the same way. Two things do not transfer. There is no 25-year option in the term dropdown, which is the UK norm, and the property tax field expects an annual percentage of the purchase price, which is how US property tax works rather than Council Tax. Enter the initial product rate rather than the APRC, since the APRC already annualises fees and compounding.
Should I put down more than 20%?
Above 20% the calculator stops charging PMI, so that threshold is where the biggest single saving sits. Beyond it, every extra percentage point simply shrinks the loan and the interest on it. What the tool cannot weigh is what else that cash could be doing, so do not drain your emergency fund to move the slider — the payment saving is visible and the risk of having no buffer is not.
Is a 15-year mortgage better than a 30-year one?
A 15-year term costs far less in total interest and builds equity much faster, at the price of a much larger monthly commitment that you cannot reduce later. The comparison table in the calculator applies your single entered rate to all four terms, which flatters the 30-year, because shorter mortgages are normally priced lower — 6.01% against 6.69% in the US in early August 2026. If you are choosing between them, re-run the calculator once per term with the rate actually quoted for that term.
Does the calculator handle overpayments or extra monthly payments?
No. The amortisation schedule assumes exactly the scheduled payment every month for the whole term, with no lump sums, no biweekly schedule, no offset account and no redraw. Overpayments are the single largest lever most borrowers actually have, and they are entirely absent here, so treat the total interest figure as a ceiling rather than a forecast.
Does this tell me how much house I can afford?
Not on its own — it never asks for your income or your other debts. The common US underwriting guideline is that housing costs stay under 28% of gross monthly income and total debt payments under 36%. Take the monthly total from this calculator, divide it by 0.28, and you have the rough gross monthly income that guideline implies; the debt-to-income calculator does the other half properly.
Why does the property tax figure never change over 30 years?
Because it is a flat percentage of the price you typed, divided by 12, and nothing in the tool ever revalues the property or moves the rate. Real assessments and millage rates change most years, and insurance premiums have been rising faster than general inflation, so the monthly total shown is a year-one estimate rather than a level cost for the whole term.
Does the calculator send or store anything I type?
No. Every figure is calculated in your browser as you move the sliders, nothing is submitted anywhere and nothing survives closing the tab. The currency symbol comes from your browser locale or a saved preference — it is a label only, and no conversion is applied to any number you enter.
Where to go next
Read next
- The complete mortgage calculator guideHow to read every figure the calculator produces, and the ones it leaves out.
- Build a household budget, step by stepWhere a mortgage payment sits once the rest of the month is accounted for.
- How much emergency fund do I need?What to keep back rather than push into a larger deposit.
- Strategies for a higher credit scoreThe single input that most changes the rate you are actually offered.
- How to split bills with a partnerDividing a joint mortgage payment when incomes are not equal.
- The 50/30/20 budget rule explainedA quick sanity check on whether the payment leaves room for anything else.
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