Attach Rate
The proportion of customers who buy an additional product or module alongside the primary one.
What it measures
Attach rate is the proportion of primary sales that also include a specified secondary product — an add-on module, a services package, a support tier. It is a measure of how reliably one thing sells alongside another, which makes it useful for capacity planning and for spotting where a bundle is doing work that a discount is actually doing.
Attach rate = deals including the attached product ÷ deals including the primary product, over the same period and the same segment.
The denominator is the whole argument
How to measure yours
Define eligibility first. A customer on a plan the add-on does not support was never a candidate, and including them understates the rate in a way that varies with plan mix rather than with performance.
Fix the period to the primary sale, not the attachment. An add-on sold three months later is expansion, not attach, and counting it as attach flatters the number while hiding the follow-on motion.
Segment before comparing. Attach rate almost always differs by deal size and by channel, so a blended figure moves when mix moves even if nothing about selling changed.
Check discount correlation. If attached deals carry systematically larger discounts, the attach rate is measuring price concession rather than demand.
Where it misleads
A rising attach rate with flat total revenue usually means the add-on is being given away to close the primary sale. Read it against realised price, not just volume.
Mandatory or auto-included components produce an attach rate near 100% that says nothing. If it cannot be declined, it is packaging, not attachment.
The metric is blind to whether the attached product is used. A high attach rate with low adoption is a renewal risk being recorded as a sales success.
Mix changes move it without any behaviour changing. A quarter weighted towards a segment that rarely attaches will show a decline that no amount of coaching would have prevented.
RELATED TERMS
Expansion Revenue
Additional recurring revenue from existing customers: more seats, higher tiers, additional products or increased usage.
Bookings
The total value of contracts signed in a period, regardless of when revenue is recognised or cash collected.
Average Deal Size
The mean value of closed-won opportunities over a period. An input to pipeline velocity and capacity planning.
Upsell
Selling an existing customer a higher tier or a larger commitment of what they already buy.
COMMON QUESTIONS
- How do you calculate attach rate?
- Divide the number of deals containing the attached product by the number of deals containing the primary product, over the same period. The decision that matters is the denominator: restricting it to deals where the add-on was actually eligible is the only version that measures selling behaviour rather than plan mix.
- What is a good attach rate?
- There is no transferable figure, because attach rate depends almost entirely on what is being attached and whether it can be declined. A mandatory component approaches 100% and means nothing; a genuinely optional module in a competitive category may be strong at 20%. The useful comparison is against your own prior periods and across your own segments, not against a published benchmark.
- Is attach rate the same as upsell?
- No. Attach happens at the point of the primary sale; upsell happens afterwards to an existing customer. Counting a later add-on purchase as attach inflates the figure and, more damagingly, hides the performance of the expansion motion that actually produced it — two different teams often own the two.
- Why did our attach rate fall without anything changing?
- Most often mix. Attach rate varies by segment, deal size and channel, so a quarter weighted towards a segment that rarely attaches will show a decline produced entirely by the composition of the pipeline. Segment the figure before concluding that selling behaviour changed.
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