The method

How we work out your figures

Everything Mortgage Meadow shows you is worked out from the figures you type in, using the model below. It’s deliberately a simple one — simple enough that you can check it — and that means it won’t match your lender to the penny.

The model

Interest is applied monthly

To the balance at the start of each month, at the rate you entered. Many lenders calculate interest daily. Over a full term that difference is real but small; it means our figure and theirs will never be identical. The contractual payment is quoted to the penny, rounded up, the way a lender quotes it, so the final payment of a term is adjusted by a few pence — a little smaller, or a little larger — rather than leaving pennies behind.

A balance you state is where the replay starts

If you tell us what is left, we replay the mortgage from that figure, on the date you gave it, rather than from the day it began. A payment dated before that date is treated as already inside the figure and is not applied again. A payment dated on that date, or after it, is counted as new. One exception in the month the figure was stated: a regular payment dated after that month began but before the date you gave is taken to be that month's payment, already reflected in the figure, so we do not assume a second one at the month's end.

Payments are in arrears

A month accrues interest first, and the payment that settles it is made at the end. So the payment for your first month falls one month after the start date, not on it. If your direct debit goes out on a different day of the month from the one the mortgage started, tell us the day in Settings: the months are then counted from that day, so a payment on the 15th settles the month that ends on the 15th rather than being read as late.

We never assume you've paid

If a month has gone by and nothing is logged against it, we don't pretend a payment happened — interest accrues and the balance goes up. Most apps quietly tick off your standing order. Telling you a month was paid when it wasn't is worse than an awkward number. Log the payment and it settles.

Your rate is held as you entered it

Until you tell us it changed. We don't predict rate movements, because nobody can.

We never assume a payment you haven't made

Not in a month you didn't log, and not in the future either. If your rate falls, the forecast falls with it — carrying on at the old higher figure would be assuming you volunteer the difference every month, and then calling that a saving. The forecast never pays more than your lender is asking for.

If you fall behind, the date moves

We don't quietly raise your monthly payment to make the original end date come true. Months that weren't paid for are months of interest, and the date moves out to match. If the balance is going up rather than down, we say that instead of giving you a date.

An overpayment reduces the term, not the payment

That's the common arrangement and it's the one that saves the most interest — but lenders differ, and some reduce the monthly payment instead unless you ask. Check which yours does.

A rate change resets the sums on what's left

When a new rate starts, the monthly payment is recalculated from the balance you actually have on that date — the same thing your lender does. That has a side effect if you overpay during a fixed period: because the balance is smaller when the new rate arrives, some of the benefit comes back as a smaller monthly payment from that date rather than as months off the term. You save interest either way, but the same lump sum paid after your final rate change takes more time off. Where a payment you're entering would be absorbed like this, the preview says so before you log it.

Early repayment charges come from the bands you enter

The figure on the dashboard is what a full redemption would cost today — clearing the whole balance, not overpaying part of it. Those are very different amounts, and the second one is usually far smaller.

The penalty-free allowance is the one you tell us

Enter the percentage your deal lets you overpay each year, and what it is a percentage of, and the what-if simulator shows how much of a plan falls inside it, and what a charge on the rest would come to. We never assume a figure — not even the common ten per cent — because a number we invented is a number you would rely on. The allowance year runs from the date you choose: the mortgage anniversary, 1 January, or a date your offer names — some lenders start the clock on the first of the month after completion. Anything overpaid before that clock starts is counted against the first year’s allowance rather than treated as free. Your mortgage offer governs.

What a sale would leave you with is your own figures, not ours

Put in what you believe the home is worth and what selling will cost — the agent's percentage, the conveyancing, anything else — and we take those, any early-repayment charge and the balance off the price. We don't value homes and we don't know what an agent charges, so nothing there is filled in for you: there's no typical fee and no standard cost. Where a figure is missing the card says which one, because every cost we haven't been told about makes the result look better than it is.

House prices are held where you put them

We don't forecast them, for the same reason we don't forecast interest rates. Your value stays exactly as you entered it — including when it's a few months old, because moving it on for you would be us valuing your home. If you want to see what a rise or a fall would do, you set the figure and it's your assumption. The agent's percentage is then taken of that changed price, so a higher price brings a higher fee with it.

“In profit” means the sale returns what you put in

The deposit and what buying cost you — stamp duty, the conveyancing, the survey. The date is the first month the sale would cover all of that after the mortgage and the costs of selling, priced month by month at the charge band in force in that month. If it's covered already we say so rather than inventing a date, and if it isn't covered by the time the mortgage clears we say that instead of quoting a house price decades out. Mortgage payments made along the way are not counted as money to get back: they bought you somewhere to live.

What counts against that allowance

An overpayment counts in full. A payment logged as a total counts only for the part above the contractual amount. Where the allowance is a percentage of the balance at the start of each year, it is worked out from the balance the modelled plan would actually leave — so a bigger plan means a smaller allowance in the years after, which is what your lender would apply too. A modelled plan starts today at the earliest: it never credits months that have already gone.

What we leave out

Arrangement fees, product fees, valuation and legal costs, and anything else that isn’t a payment against the balance. None of it is included unless you enter it. A projection is a forecast of one thing — the balance — not the total cost of owning a home.

Which figures are authoritative

Your lender’s. Their statements and their calculations are the record of your mortgage. Where they differ from Mortgage Meadow, they are right and we are not. We’re a way of seeing the shape of it and trying out an idea before you commit — not a substitute for your lender’s numbers, and not financial advice.

Mortgage Meadow is not authorised or regulated by the Financial Conduct Authority. Nothing here is a recommendation about your mortgage. If you want one, speak to a mortgage adviser authorised by the FCA — you can check a firm on the Financial Services Register.

Keep your own copy

Your figures are encrypted on your own device before they reach us, so we hold a copy we can’t read — and can’t restore for you if you lose your passphrase and your recovery code. We’d suggest exporting your payments now and then and keeping the file somewhere safe. It’s yours, it opens in a spreadsheet, and it means you’re never dependent on one device or on us.

Guides: how overpaying works · ← Back to the tracker

Page last updated 23 August 2026