How to calculate average order value from Shopify orders

What is average order value?

Total sales divided by the number of orders over the same window. Two fields, one division. The arithmetic is trivial and the reporting is where it goes wrong.

The mistake nearly everyone makes

There are two ways to compute AOV over a week and they give different answers.

Weighted. Sum the week's sales, sum the week's orders, divide.

Unweighted. Compute each day's AOV, then average the seven numbers.

The first is correct. The second treats a Sunday with two orders as equal in weight to a Black Friday with two thousand, and a single quiet day with one expensive order can move it by a third.

// Right.
const aov = totalSales / totalOrders;

// Wrong, and it will look plausible for months.
const aov = days.reduce((sum, d) => sum + d.sales / d.orders, 0) / days.length;

This is also why a correct AOV chart looks inconsistent: each point is that day's own ratio, and the headline is the window's ratio. They are not supposed to match, and a tool whose headline equals the mean of its points is doing the wrong calculation.

Getting the two numbers

One GraphQL query gives you both, because the order count is the number of nodes you summed.

query Orders($query: String!, $cursor: String) {
  orders(first: 250, query: $query, after: $cursor) {
    pageInfo {
      hasNextPage
      endCursor
    }
    nodes {
      createdAt
      displayFinancialStatus
      currentTotalPriceSet {
        shopMoney {
          amount
          currencyCode
        }
      }
    }
  }
}

Count the nodes you include in the sales total, and divide at the end. Count and sum have to use the same filter, or the ratio is meaningless.

Decide about cancelled and refunded orders once

An order that was placed and then refunded happened. It had a value. Include it in both numerator and denominator and your AOV is the average value of orders placed.

Exclude it from both and your AOV is the average value of orders kept. Also defensible.

What is not defensible is excluding it from one and not the other, which is the easiest bug to write here: filter the sales sum on financial status and forget to filter the count, and the AOV quietly drops.

Currency

shopMoney is in the store's currency. A store selling in several presentment currencies still has one shop currency, so this is already normalised and the division is safe.

If you are summing presentmentMoney for some reason, AOV across mixed currencies is a number with no units.

What actually moves AOV

Three things, and they call for different responses.

Price changes move it evenly across every order.

Bundles and upsells move it only for the orders that take them, so AOV rises while the median order stays put. Worth watching the distribution, not just the mean.

One wholesale order moves it for a day and then it falls back. If a single order can move your AOV visibly, the mean is the wrong statistic and you want the median.

In the notch

Notch Metrics reports Shopify average order value as sales divided by orders over the whole window, with each sparkline point being that day's own ratio. The page says so, so the apparent inconsistency is documented rather than discovered.

Place it beside sales and orders and the three explain each other. Everything Shopify reports, or download Notch Metrics.