Upselling means selling an existing customer more of, or a higher tier of, what it already buys. Measured as the increase in revenue on a line the customer already bought, period against period, floored at zero. Downsell is the decrease. Where quantity is held, upsell splits into volume and price, because a price rise counted as upsell flatters the team.
Upselling is getting a customer to buy more of a product it already takes, or a bigger or higher-tier version of it. Selling it a different product is cross-selling. As a measure, upsell is the revenue growth on lines the customer already held.
For lines the customer holds, the difference between its spend and what similar customers spend on that line.
Expansion of two percent can be fourteen points of new lines and eighteen points of shrinkage on old ones.
Upsell per line = max(0, revenue this period − revenue last period), on lines the customer already bought, summed across lines. Decreases are reported separately as downsell.
A customer's spend on fixings rose from $30,000 to $41,000: upsell of $41,000 − $30,000 = $11,000. Its spend on adhesives fell by $6,000, reported as downsell, not netted.
Netted against downsell. A base with heavy movement in both directions looks static.
For both measures on one customer base, see cross-sell and upsell.