Page speed and sales — your numbers, not averages
A slow site is the subject with the largest number of other people percentages circulating around it. This calculator knows none of them: the number saying how much conversion one second is worth is entered by you.
Without that field no result appears, and that is deliberate. Putting an industry average there would turn a measurement into a forecast, and our tools do not do that. Your current LCP can be measured with our free audit.
Page speed and sales — your numbers, not averages
The time the largest element on screen appears. Measure it with our free audit.
This is your assumption — ideally from your own test. We have no number to put here and deliberately do not invent one.
Fill in every field — without them there is nothing to calculate. We substitute no default values, because each of them would be our assumption rather than yours.
How to read this result
You enter the conversion lift per second — and that is deliberate
It is the one number in this calculator that cannot be borrowed from someone else's measurement. It depends on the industry, the price, the traffic and what people came to the site for. Substituting an “average” here would turn the whole calculation into a forecast, and we do not make those.
Deloitte for Google, “Milliseconds Make Millions” (2020) — 37 European and US brands, over 30 million mobile sessions: a 0.1 s speed improvement went together with an 8.4% rise in retail conversion. — this is averaged statistics from other websites; we give it as a reference point, not as a value to type into the field
Faster does not mean 100/100
Chasing a perfect score in measurement tools usually means removing animation, images and features that help you sell. The sensible target is the good-loading-time threshold with the functionality intact, not the highest number in a report.
Where to get your own number
From your own data: comparing conversion between faster and slower pages, real-user measurement data, or an A/B test after the change. Until such a number exists, this calculator is for checking what assumption would make the change pay for itself at all.
This is arithmetic from the assumptions you entered, not our forecast. Every number in the result comes from the fields above — there are no market averages and no estimates of ours in it.
You have the numbers. Let us talk about them.
Pick a time for a call or leave your number — we will go through your assumptions together and say which of them do not hold up in practice.