Shopify Sales Velocity Formula: Calculate It in 30 Seconds

Most Shopify sellers track two inventory numbers: current stock and revenue. Neither one tells you when you're about to run out.

Sales velocity - the number of units you sell per day - is the missing piece. It's what turns a stock count from a static snapshot into an actionable signal.

What is sales velocity (and why stock count alone is misleading)

Sales velocity is how fast a product moves. Measured in units per day (or per week for slow movers), it's the speed at which your inventory depletes.

Here's why stock count alone misleads you:

Product A: 200 units in stock, sells 1 per day = 200 days of stock. Completely fine. Product B: 200 units in stock, sells 50 per day = 4 days of stock. Critical situation.

Same inventory number. Completely different urgency. Without knowing the velocity, 200 units looks identical for both products. With velocity, you know one needs immediate attention and one can be ignored for months.

This is why "I check if stock feels low" fails as a system. Your gut is calibrated to the number, not the velocity.

How to calculate daily sales velocity

The basic formula:

Daily Sales Velocity = Total Units Sold / Number of Days

If you sold 150 units of a product in the last 30 days, your velocity is 5 units per day.

Which time window to use matters:

• Last 7 days: good for fast-moving products or anything trending. Very sensitive to recent changes.
• Last 30 days: solid baseline for most products. Smooths out day-to-day noise.
• Weighted 14-day average (recent days count 2x): best of both. Captures current trends without overreacting to a single spike day.

The weighted calculation:

1. Take your last 14 days of sales
2. Multiply sales from days 1-7 (most recent) by 2
3. Add that to days 8-14 (single weight)
4. Divide by 21 (7 days x 2 weight + 7 days x 1 weight)

Example: last 7 days sold 84 units total (12/day average), days 8-14 sold 42 units total (6/day average).

Weighted velocity = (84 x 2 + 42) / 21 = 210 / 21 = 10 units/day

This gives more weight to recent sales while keeping the older period in the picture.

Where to find this data in Shopify

Go to Analytics > Reports > Sales by product variant. Set the date range to the last 30 days, export to CSV.

You'll get total units sold per variant. Divide by 30 to get daily velocity.

Shopify doesn't display velocity directly - you have to calculate it. This is one reason manual tracking breaks down at scale. Doing this calculation for 200 SKUs every week is not something most sellers do consistently.

4 things sales velocity tells you

1. When you'll run out of stock

Days Until Stockout = Current Stock / Daily Velocity

Product with 80 units at 5/day velocity = 16 days of stock. Same product at 20/day velocity = 4 days of stock.

This single calculation, done for every product, replaces the "check if it feels low" approach with an actual number.

2. When to reorder

Combine days until stockout with your supplier lead time:

Reorder Date = Today + Days Until Stockout - Lead Time Days

If you stock out in 16 days and your supplier takes 10 days, you need to reorder within 6 days. If you have 4 days of stock and lead time is 10 days, you needed to reorder 6 days ago.

This is the core of the reorder point formula covered in How to Calculate Your Reorder Point on Shopify.

This breaks down fast if part of your velocity comes from wholesale orders instead of storefront checkouts - a bulk order can drain stock without showing up as a spike in your daily sales report. See our guide on managing wholesale orders on Shopify without multiple warehouses for how to track both channels at once.

3. Which products deserve your attention

Map your products on two dimensions: velocity and current stock level.

• High velocity + low stock = urgent, needs action today
• High velocity + high stock = healthy, monitor weekly
• Low velocity + low stock = fine, plenty of time
• Low velocity + high stock = potential dead stock, worth reviewing — see our guide on finding and fixing dead stock on Shopify

Your top 20% of products by revenue likely sit in the high-velocity category. These deserve the most attention and the tightest reorder points. ABC analysis formalises this split — categorising every SKU by revenue contribution so you know exactly which products need the tightest monitoring.

4. Whether a trend is emerging

Compare this week's velocity to last month's average. If a product's 7-day velocity is 50% or more above its 30-day average, something is happening.

A TikTok mention. A competitor going out of stock. A seasonal shift. A new channel driving traffic.

You want to know about velocity spikes before you stock out, not after. A product that normally moves at 8/day suddenly moving at 35/day changes your entire reorder timeline. What was 20 days of stock is now 4 days.

Common mistakes with sales velocity

Using all-time averages. A product you've sold for 18 months has very different velocity now versus when you launched it. All-time averages bury current trends under historical data.

Ignoring out-of-stock days. If a product was out of stock for 10 days last month and you sold 60 units in the other 20 days, your real velocity is 3/day - not 2/day. Out-of-stock days should be excluded from the calculation, but most sellers don't do this.

Treating seasonal products the same as evergreen ones. A product that sells 20/day in November and 3/day in March needs a seasonal adjustment to velocity calculations. Applying the annual average in either direction will give you the wrong reorder point.

Automating velocity tracking

Calculating velocity manually for a handful of products is manageable. For 50+ SKUs with different velocity patterns, seasonal adjustments, and weekly updates needed - it becomes a part-time job.

Debnix calculates velocity per product automatically using your Shopify sales data, applies weighted recent-vs-historical calculations, and surfaces products where velocity is spiking before they become a problem. 7-day free trial, no credit card.

For setting up alerts based on velocity, Shopify Inventory Alerts: Get Notified Before Stockouts covers the options from free to paid.

TL;DR

• Sales velocity = units sold per day. It tells you how fast inventory is depleting.
• 200 units of stock means 200 days if velocity is 1/day, or 4 days if velocity is 50/day
• Use last 30 days for stable products, last 14 weighted 2x for trending products
• Velocity tells you: days until stockout, when to reorder, which products need attention, and whether a trend is emerging
• Avoid using all-time averages - they bury current trends
• Above 50 SKUs, manual velocity tracking isn't sustainable