How to Measure the ROI of a Website Redesign

A new website is an investment, and like any investment you should be able to say whether it paid off. Too often, nobody can: the numbers moved after launch, but nobody knows which changes caused what, or what "good" looked like before. Here's how to measure a website redesign's return properly, from baseline to attribution.

The ROI formula

ROI = (value gained − cost) ÷ cost × 100%

The cost side is easy: design, development, content, tools and your team's time. The value side is where most measurement falls apart, so most of this guide is about that.

Step 1: Set a baseline before launch

Record your current numbers for at least a few months before the new site goes live:

• Visitors and where they come from
• Conversions: enquiries, sales, bookings, sign-ups
• Conversion rate by key page and device
• Revenue from the website, if it sells
• Search visibility: impressions, clicks and top queries in Google Search Console
• Page speed and Core Web Vitals
• Support or sales questions the site should answer

If your business is seasonal, keep at least a year of history so you can compare the same months. Our guide to Google Search Console shows where to find the search figures.

Step 2: Choose metrics that match your goals

Pick two or three primary metrics; tracking twenty means nobody acts on any.

Step 3: Put a value on conversions

If the site doesn't sell directly, estimate what each conversion is worth:

Value per enquiry = close rate × average deal value

For example, 25% of enquiries become customers worth £2,000 each, so each enquiry is worth about £500. Ten extra enquiries a month adds about £5,000 a month.

Step 4: Attribute changes to the work

This is the hard part. Numbers move for many reasons: seasonality, marketing campaigns, competitors, algorithm updates. To link results to specific work:

1. Record when each change shipped: new checkout, speed fixes, rewritten service pages.
2. Compare against the baseline for the pages and metrics each change should affect.
3. Check for other causes in the same period, such as ad spend changes or press coverage.
4. Use annotations in your analytics so ship dates are visible on charts.
5. Label correlation honestly. "Sign-ups rose 24% in the month after the new checkout launched" is a fair statement; "the checkout caused a 24% rise" needs more evidence.

Step 5: Calculate and report

Combine value gained over a fair period, three to twelve months, against the full cost. Report it with the assumptions written down: value per conversion, the period, other factors. A transparent estimate is more credible than a precise-looking number.

A worked example

A consultancy spends £18,000 on a redesign, plus £1,000 of staff time.

Baseline (average of the six months before launch): 2,000 visits a month, 1.5% enquiry rate, so 30 enquiries a month. 25% become clients worth £2,000 each on average.

After launch (months 4–9, once rankings settled): 2,400 visits a month at a 2.2% enquiry rate, so about 53 enquiries a month.

Over twelve months, the extra value is roughly £138,000 against a £19,000 cost, before any other factors. Even if half the improvement had other causes, such as a marketing push in the same period, the return would still be substantial. Writing that caveat down is what makes the number credible.

Tracking setup checklist

Before launch, make sure you can measure:

• Analytics installed on every page, with conversions configured (form submissions, purchases, bookings, calls)
• Google Search Console verified and connected
• UTM parameters on campaign links; see UTM parameters explained
• Call tracking or a distinct number if phone enquiries matter
• A way to know which enquiries became customers, even a simple spreadsheet
• Annotations for launch and each major change
• Baseline figures saved somewhere that won't be overwritten

Reporting ROI to stakeholders

Keep it to one page:

1. The goal the redesign was meant to achieve.
2. Before and after for two or three primary metrics.
3. The value of the change, with the assumptions written out.
4. The cost, including staff time.
5. Other factors that may have contributed.
6. What's next: the improvements most likely to add more value.

A clear, honest page builds more confidence than a dashboard full of charts.

Leading indicators to watch in the first month

Full ROI takes months, but early signs tell you whether you're on track:

• Conversion rate on key pages
• Mobile vs desktop conversion
• Page speed and Core Web Vitals
• Indexing: are the new pages in Google?
• Bounce from high-traffic landing pages

If these look healthy, the longer-term numbers usually follow.

Common mistakes

• No baseline, so improvements can't be shown.
• Measuring too soon, before search rankings settle.
• Vanity metrics, like visits without conversions.
• Ignoring cost savings, such as fewer support calls or faster content updates.
• Claiming every rise, including ones caused by something else.

Small changes compound

ROI doesn't stop at launch. Ongoing improvements, such as faster pages, clearer copy and fixing UX mistakes that kill conversion, keep adding value.

How Zelvorm proves impact

Zelvorm's Proof-of-Impact Ledger connects a client's analytics, Search Console and revenue data, sets a before baseline and links changes in the numbers to the specific deliverables behind them, clearly labelled. At the end of a project, clients get a shareable Project Wrapped summarising what shipped and what moved.

The short version

Record a baseline before launch, choose two or three metrics tied to your goals, value each conversion, link changes to ship dates honestly, and judge ROI over months, not days.