About
What this is, and how it actually works.
You're being asked to hand your financial details to a tool you've never heard of, so here are the answers to the questions worth asking first.
Where it came from
I built this for me and my partner.
We were looking for our first house and I kept hitting the same wall. A mortgage calculator will tell you the repayment, which is genuinely useful and also about a third of the answer. It has nothing to say about council tax, which varies more between areas than I'd assumed, or what a particular house costs to heat, or whether either of us would still be fine with the commute once it was dark and raining.
So I started a spreadsheet, the way you do. For a while it was just a few houses side by side with sensible costs attached. Then I added the bills. Then commute times, because we kept disagreeing about how far was too far, and then a rough score so we could stop going round in circles and point at the same number instead.
It got out of hand, and the thing a spreadsheet is worst at was by then the thing we needed most, which was for both of us to be looking at the same figures on the same day, with the costs divided in a way that reflected two fairly different incomes rather than an automatic half each.
So I built the thing my spreadsheet had been badly imitating. There's no search in it and it isn't trying to be a portal. It picks up at the point where you've already found somewhere you like and want to know whether the numbers behind it hold up.
How it works
Eight steps, in the order you'd meet them. Roughly speaking, you tell it what your life costs and it works out what each house would add to that.
01Start with your finances
The unglamorous part, and it's about you rather than any house. Your monthly take-home pay, whatever deposit you've managed to put together, any regular commitments that aren't housing, and a target for how much you'd like to still have at the end of a month once everything's been paid.
The take-home figure and that leftover target do most of the work later on, since nearly every number the app produces gets measured against one or the other. Your deposit can come from more than one place and it adds them up for you, so a Lifetime ISA sitting alongside help from a parent doesn't need reconciling into a single figure first.
02Set your bill defaults
Then the running costs you expect a house to have. Gas and electricity, water, broadband and groceries, along with the mortgage rate and term you want to assume until you know better.
The important thing about these is that they're global. They apply to every property you add, so changing one here recalculates your entire shortlist at once. That's usually what you want, though it does mean a bad guess spreads quietly.
They're your numbers as well, not ours. We don't look them up anywhere and we've no way of checking them against a real bill. Whatever you type is what the maths runs on.
03Why we suggest setting those high
Nobody can tell you what a specific house will cost to run before you've lived in it through a winter, and that includes us. Too much of it comes down to the building itself, the tariff you end up on and how warm you like your rooms. Rather than pretend to a precision we haven't got, we'd rather you were deliberately gloomy.
Pitch each default at the worst you'd still be willing to pay rather than what you're hoping for. An old boiler behind thin walls will cost you far more than a modern flat does, energy prices move around more than anyone would like, and broadband that looks cheap today is usually only cheap for twelve months. If a budget only works at the bottom of every range then it doesn't really work.
There's a compounding version of this too, because a default lands on everything at once. An optimistic figure doesn't flatter one house, it flatters all of them, and it does it quietly enough that you'd have no particular reason to notice. The suitability score is built on these same numbers, so a property that still holds up on pessimistic figures is genuinely comfortable, while one that only looks good on hopeful ones is thinner than it appears.
Being wrong in this direction costs you nothing. If the real bills come in under, you've more room than you thought, whereas being £40 out on three of them is nearly £500 a year you hadn't planned for.
04Add the properties you're looking at
You can type a property in by hand, though most people don't. Upload a screenshot of the listing and it'll pull the details out for you to check over, or install the browser extension and import straight from Rightmove, Zoopla or OnTheMarket without leaving the page you're already on. Nothing saves by itself whichever route you take, so you always get a look at what's about to be added.
Council tax is the one figure fetched for you. It comes from your actual local council rather than a national average, matched against whatever band the listing mentions. If there's no band it assumes D and tells you so, and you can correct it once you find out.
05Adjust anything that doesn't fit that house
This is what makes a cautious default liveable rather than irritating. Any bill, the mortgage rate, the term and any of your commitments can be overridden on a single property without disturbing anything else you're weighing it against.
Say your energy default is a deliberately grim £250, and then you find somewhere rated EPC A with a boiler fitted last year. Drop it to £175 on that house alone and everything else on your list carries on being judged against the pessimistic figure. The same works in reverse for a draughty Victorian terrace, or when a broker comes back with a real rate for one specific purchase.
Commitments behave the same way, which turns out to be the more interesting use of it. If the only way a house works is by cutting your holiday fund from £500 to £300, you'll see that straight away, on that house, without having to pretend you've made that decision everywhere else.
06What each property is scored on
All of that collapses into one number out of 100, weighted 65% on affordability and 35% on location.
The affordability side compares your monthly leftover against the target you set, but not on a straight line. Falling short is penalised harder than a simple ratio would, because being under target compounds in real life rather than easing off. If there's nothing left at all once the house is paid for, the score is zero however perfect the location might be.
The location side works off the places you've saved. For each one it measures the drive and the walk against your ideal time for that mode and keeps whichever comes out better, so somewhere you'd never dream of walking to isn't punished for being a long walk. Hitting your target exactly gives you 80, beating it climbs towards 100, and going over falls away gradually rather than off a cliff. With several places saved it averages their best scores.
07If you're buying with someone
Link two accounts and you get one shared list of properties, a combined deposit, and costs divided however you've agreed rather than an assumed half each. Commute scores stay individual, since you rarely both work in the same building.
Worth knowing before you do it, linking shares more than totals. Your partner will be able to see raw income and take-home pay. It's opt-in and you can undo it, but read what's involved beforehand rather than after.
08What it won't do
Every number here is worked out from something you typed. None of it is checked against your actual bank, your credit file or a lender's view of you, and none of it is financial advice or a mortgage offer. It won't recommend a house and it holds no opinion on which one you should buy.
What it does is arithmetic you could do yourself, on properties you've already found, faster and in one place. How good that arithmetic turns out to be depends entirely on the numbers you feed it, which is why step three matters more than it looks.
What's stored and what isn't
Using this means handing over real financial detail, so it's fair to ask where it ends up. You make an account and type in your income, your deposit, your outgoings and the properties you're watching. It's used to run your own calculations and nothing else. It isn't sold anywhere and it's never used to train a model.
The one genuine exception is partner linking. Once you're linked, much of what you've entered becomes visible to the other person, and that includes raw income and take-home pay rather than only totals. It happens solely because you've sent or accepted an invite, and the full itemised list of what crosses over is in the privacy policy.
Signing in runs through Clerk and payments through Stripe. Neither of them sees your financial profile, only the piece each one needs to do its job.
Delete your account and the data goes with it, usually well inside 30 days, and you can ask for that at any point by getting in touch.
Common questions
Who is this for?
Anyone actively looking to buy who wants a clearer picture of what each property would really cost them. There's some setup at the start, since you enter your income, deposit and bills yourself rather than having anything pulled in from your bank. It takes a few minutes, and it's where all the useful numbers come from.
Does it work on mobile?
Yes, and a lot of work has gone into making sure it does properly, from navigation through to how forms and modals behave on a small screen. Desktop still gives you more room, particularly when you're comparing several properties against each other, so a laptop is the natural place to sit down with a shortlist. But mobile isn't just good enough for checking something on the train any more. You can genuinely run the whole thing from a phone.
How do I add properties?
However suits you. Typing one in by hand takes about thirty seconds if all you want is the address and price. You can also upload a screenshot of a listing and we'll pull the details out for you to look over before anything saves. Easiest of all, if you're on Rightmove, Zoopla or OnTheMarket, is our browser extension, which adds a button to the listing page and sends the title, address, price, bedrooms, bathrooms, council tax band and coordinates straight across, so you arrive with the form already filled in. Nothing ever saves on its own, so you always see the details first.
Where does the property data come from?
From you, one way or another. You either enter it, screenshot it, or import it with the extension while you're sat on the listing page. We don't scrape Rightmove or Zoopla ourselves because their terms don't allow it. The calculations built on top of it are all ours.
How is the monthly mortgage payment calculated?
We use a standard repayment mortgage formula based on the property price, your deposit, the interest rate, and the term. You set a default rate and term in your profile and can override them per property. The result is a monthly repayment estimate, not a guarantee or a mortgage offer.
What is the suitability score based on?
Affordability is 65% of it and location fit the other 35%. The affordability half compares your monthly leftover against the target you set, using a curve that comes down harder on falling short than a straight ratio would. For location, we take each place you've saved and measure both the drive and the walk against your ideal time for that mode, then keep whichever of the two scores better, so somewhere you'd always drive to isn't penalised for being a long walk. Hitting your target time exactly gives you 80, beating it scales up towards 100, and going over decays gradually rather than dropping off a cliff. With more than one place saved we average their best scores. If your leftover goes negative once everything's paid, the score is zero no matter how good the location is.
What does 'ideal leftover' mean?
It's the percentage of your monthly take-home you want to still have once the mortgage, the council tax and every other housing cost has gone out. You set it in your profile, and the affordability score is measured against it on a curve rather than a straight line. Hit your target exactly and you score 100, but come in 20% under and you'll score around 64 instead of the 80 a simple ratio would give you, because being short compounds in practice rather than easing off.
Why does the tool suggest overestimating bills?
Because being wrong in that direction is free and being wrong in the other direction isn't. Energy prices move around, water rates vary by region and cheap broadband is often only cheap for a year, so a budget built on best-case figures tends to stop working about the time you've finished unpacking. Set them high and anything cheaper is a bonus. We'd much rather a property looked comfortable on pessimistic numbers than have you move in and discover the maths only ever worked if everything went right.
Can my partner and I both use this for the same properties?
Yes, and that's really what partner linking is for. One of you subscribes to premium at £6.99 a month and links the other, after which you share a property list, a combined deposit total and costs split by whatever ratio the two of you have agreed. Commute scores stay personal to each of you, worked out from your own saved places. Linking does share a lot, raw income and take-home pay included, so read what's involved in the privacy policy before sending or accepting an invite.
What happens to my data if I cancel or delete my account?
It gets deleted. We aim to have your personal and financial data out of our active systems within 30 days of the account closing, and we don't hold onto it afterwards. You can ask for deletion whenever you like by getting in touch.
Is this regulated financial advice?
No, and it's important that's clear. This is a budgeting and planning tool rather than a financial adviser or a mortgage broker. Everything it produces is an estimate worked out from what you entered, none of it verified against your real finances, and nothing here amounts to advice or a mortgage offer. If you want actual mortgage advice, speak to a whole-of-market broker, and plenty of them will do a first consultation for free.
Does this work outside England?
Not at the moment. Council tax is set locally and works differently in Scotland, Wales and Northern Ireland, so for now the tool only supports properties in England.