Design improves conversions when it makes it easy for the right visitor to find what they came for and take the next step, on a page that loads fast and works on a phone. Nobody can promise to double your rate, and we do not. What reliably helps is picking the one task each page exists for, removing what gets in the way, meeting the Core Web Vitals targets, and testing with a handful of real users before and after launch. Choose a design partner by how they work and measure, not by their portfolio alone.
Key takeaways
- Nielsen Norman Group's point for e-commerce is blunt: "if users cannot find the product, they cannot buy it either".
- Google's "good" Core Web Vitals targets are Largest Contentful Paint of 2.5 seconds or less, Interaction to Next Paint of 200 milliseconds or less, and Cumulative Layout Shift of 0.1 or less, measured at the 75th percentile of page loads.
- Nielsen Norman Group says testing about five representative users typically finds the most important problems, and recommends many small tests over one big study.
- It also suggests spending about 10 percent of a design budget on usability, and estimates this typically more than doubles quality metrics; treat that as its estimate, not a guarantee.
- Conversion work is measured: define the action, track it, change one thing at a time.
How does web design affect marketing results?
Design is where marketing's promise meets the visitor. An advert or search result sends someone to a page; the page either confirms they are in the right place and shows the next step, or it does not. Usability, as Nielsen Norman Group defines it, is how easy an interface is to use, judged by how easily people learn it, how efficiently they work with it, how few errors they make and how satisfying it is. Utility is whether it has what they need. A page must have both. Our conversion rate optimization service starts with this question for each page.
What should you fix first?
- Name the one job of each page. A service page's job is an enquiry or a booking; an article's job is to answer a question and point to the next step.
- Make that action obvious. One primary button, clear wording, visible without hunting, repeated where the reader has finished reading.
- Cut what distracts. Extra menus, rival buttons and autoplay compete with the action.
- Say what the visitor needs to decide. What you do, who it is for, how it works, what happens next, and proof you can check.
- Shorten forms to what you need to reply.
- Check the phone first. Test the real journey on a small screen.
Our landing page checklist goes through this in detail.
How fast should a page be?
Google defines three Core Web Vitals, each judged at the 75th percentile of page loads, split by mobile and desktop. A page passes when all three are good:
| Metric | What it measures | Good |
|---|---|---|
| Largest Contentful Paint (LCP) | Loading | 2.5 seconds or less |
| Interaction to Next Paint (INP) | Responsiveness | 200 milliseconds or less |
| Cumulative Layout Shift (CLS) | Visual stability | 0.1 or less |
INP replaced First Input Delay as a Core Web Vital in 2024. Heavy images, scripts from third parties and layout that jumps as it loads are the usual culprits; a design that ignores them will lose visitors before the headline is read.
How do you test a design?
Test with real people, early and repeatedly. Nielsen Norman Group's advice is to:
- use representative users, such as your actual customers;
- give them realistic tasks and watch where they succeed or struggle;
- test individually and do not help them;
- run about five users per round, which typically finds the most important problems;
- make several small tests with changes between them rather than one large study.
After launch, measure the actions that matter in your analytics, and change one thing at a time so you know what worked. See UX and UI design trends in 2026 for what is changing in interfaces.
How do you choose a web design agency?
Ask for evidence of how they work rather than promises of results.
- Discovery. Do they start by learning your customers and goals, or by showing templates?
- Measurement. Will they set up tracking for the actions that matter and report on them?
- Testing. Do they test with users, and fix what they find?
- Performance and accessibility. Do they aim for the Core Web Vitals targets and the WCAG standard?
- Ownership. Will you own the code, content and accounts, and be able to edit the site yourself?
- Honesty. Be wary of anyone who guarantees a conversion increase or a ranking.
Our website design page describes how we work, and How to hire an app development company in 2026 has a similar checklist for apps.
What about AI in design?
AI tools can help produce layouts, copy options and image drafts quickly. They do not know your customers, so every output still needs to be tested with real users and checked for accuracy and accessibility. Use them to explore, then decide with evidence.
FAQ
Can a redesign double my conversion rate?
Sometimes a redesign helps a lot, and sometimes it does little. No one can promise a figure in advance. Measure your current rate, change what the evidence points to, and measure again.
What is a good conversion rate?
It varies widely by industry, offer and traffic source, so compare your own pages with each other and over time instead of with a headline average.
How many users do I need for usability testing?
Nielsen Norman Group says about five representative users per round typically find the most important problems; run several rounds as you improve the design.
Does page speed affect conversions?
Slow, jumpy pages make the experience worse, and Google publishes targets for loading, responsiveness and stability. Aim to pass all three at the 75th percentile on mobile.
How much of a design budget should go to usability?
Nielsen Norman Group suggests about 10 percent, and estimates this typically more than doubles a website's quality metrics. Treat that as its estimate, not a promise.
Sources
- Nielsen Norman Group, "Usability 101: Introduction to Usability": https://www.nngroup.com/articles/usability-101-introduction-to-usability/
- web.dev, "Web Vitals": https://web.dev/articles/vitals
