Conversion rate and conversion volume are both important metrics for an ecommerce store, but they pull in different directions under different conditions. Improving your conversion rate (purchases divided by sessions) is not always the right goal, and neither is simply maximising conversion volume. Understanding which to prioritise — and when — leads to better decisions about campaigns, landing pages, and budget allocation.
Defining the Metrics
Conversion Rate (CVR)
CVR = Conversions / Sessions (or Users). A 3% conversion rate means 3 out of every 100 sessions result in a purchase. CVR tells you how efficiently your store converts the traffic it receives.
Conversion Volume
Total number of conversions in a period. 300 purchases in a month is the volume. Volume tells you the total business output, regardless of how efficiently you reached it.
When High Conversion Rate Does Not Mean Good Performance
Scenario: your store runs a highly targeted ad campaign to past purchasers. It drives 100 sessions with a 15% conversion rate = 15 purchases. Meanwhile, your broad prospecting campaign drives 10,000 sessions at 1% CVR = 100 purchases.
The retargeting campaign has a 15x higher CVR. But the prospecting campaign delivers 7x more purchases at likely lower CPA. Optimising purely for CVR would lead you to cut the prospecting campaign, reducing total volume significantly.
CVR can be misleading when traffic quality changes. If you narrow your audience to high-intent buyers only, CVR goes up but volume shrinks. If you open to broad audiences, CVR drops but volume may increase if the audience is large enough.
When Conversion Volume Does Not Mean Good Performance
Scenario: you reduce your product price by 30% to drive more purchases. Conversion volume goes up 40%, but revenue per order drops 30%. Volume increased; revenue may have fallen depending on the elasticity. Optimising for conversion volume without tracking revenue or ROAS can lead to decisions that hurt profitability.
Volume can be misleading when average order value changes. 200 purchases at $30 AOV is worse than 150 purchases at $75 AOV. Always pair conversion volume with revenue and ROAS.
The Right Metric for Each Decision
Landing page and UX optimisation → CVR
When testing landing page layouts, copy, product images, or checkout flow changes, CVR is the right metric. You are holding traffic quality constant (same ad, same audience) and measuring how well the page converts it. A higher CVR from the same traffic source = better page.
Campaign scaling decisions → Volume and ROAS together
When deciding how much budget to allocate across campaigns, use conversion volume and ROAS together. A campaign with lower CVR but higher volume at an acceptable ROAS should get budget. A high-CVR campaign that cannot scale beyond a small audience is capped regardless of its rate.
Audience strategy → CVR by segment
Compare CVR by traffic source or audience segment to understand relative quality. Organic search CVR vs paid social CVR tells you which channel sends higher-intent visitors. But always check volume alongside — a 10% CVR channel sending 50 sessions monthly matters less than a 2% CVR channel sending 5,000.
Smart Bidding target setting → Both
When setting a Target CPA or Target ROAS for Google Ads or Meta, the system optimises conversion volume within your efficiency target. Set targets that balance the CVR you need for profitability with the volume you need for business growth. Too tight a target = high CVR, low volume. Too loose = high volume, unacceptable ROAS.
Practical Framework for Shopify Stores
For weekly performance review:
- Check revenue and transaction count first (did the business do well?)
- Check ROAS by channel (did you get efficient volume from paid?)
- Check CVR by channel (is traffic quality changing?)
- If CVR dropped: investigate whether traffic mix changed (more cold traffic) or whether the site/offer changed
- If CVR improved but volume dropped: check whether audience narrowing is limiting scale
Neither CVR nor volume alone tells the full story. Use them together to separate efficiency from scale problems.
Book your free Shopify tracking audit here and we will help you set up the right metrics framework to evaluate campaign performance and store efficiency together.