Cash Flow Calculator

Work out the monthly and annual cash flow left on a rental once the mortgage, running costs and void allowance are taken out.

freeworks offlinenothing uploaded
Input
Output

About cash flow calculator

Cash Flow Calculator loads once and then runs on its own. Close the tab and there is nothing left behind, on the machine or anywhere else.

Load the page once and it works offline from then on. Nothing about the tool needs a connection after that first request.

You will find it under Property, alongside 12 other tools for the same sort of job.

Runs in this tab, so nothing you type is uploaded.

How to use it

01
Start it
Every control is on the tool itself. Keyboard shortcuts, where there are any, are listed beside it.
02
Watch it run
It updates in the page as you go. Nothing is sent anywhere, so it keeps working with the network off.
03
Close when done
Nothing is stored between visits. Reloading gives you a clean start rather than picking up where you left off.

Examples

A flat renting at 1,200 a month
With a 500 mortgage payment, running costs and a letting agent on 10%
Input
monthlyRent: 1200
vacancyRatePercent: 5
monthlyMortgagePayment: 500
monthlyMaintenance: 50
monthlyInsurance: 30
managementFeePercent: 10
monthlyOtherCosts: 20
Output
Effective monthly rent: 1140
Management fee amount: 114
Total monthly costs: 714
Monthly cash flow: 426
Annual cash flow: 5112

Questions

Does Cash Flow Calculator work offline?+

Yes. It is JavaScript running in this tab, so once the page has loaded it needs nothing further from the network. Put the machine in flight mode and it carries on. Nothing you do here is sent anywhere, because there is nowhere for it to go.

Does it remember anything between visits?+

No. Reload the page and it starts from nothing. There is no account, no saved state and no cookie holding your last session. That is a deliberate trade: it cannot lose your data because it never keeps any.

Is it accurate?+

Timing comes from performance.now(), the high resolution clock the browser provides, rather than from setInterval, which drifts by a few milliseconds every tick and compounds over minutes. What can still shift things is the browser throttling a tab in the background, so leave it visible if the timing matters.

Does it make a sound?+

Where a sound makes sense, it is generated with the Web Audio API rather than loaded as a file, so there is nothing to download and nothing to block. Browsers refuse to start audio until you have interacted with the page, which is why the first press is what switches it on.

Can I use Cash Flow Calculator on a phone?+

Yes. The controls are sized for touch and the layout collapses to one column on a narrow screen. Bear in mind that a phone locking its screen will suspend the page, and timing stops with it.