The incremental cost-effectiveness ratio (ICER) is a statistic used in cost-effectiveness analysis to summarise the cost-effectiveness of a health care intervention. It is defined by the difference in cost between two possible interventions, divided by the difference in their effect. It represents the average incremental cost associated with 1 additional unit of the measure of effect. The ICER can be estimated as:

${\displaystyle ICER={\frac {(C_{1}-C_{0})}{(E_{1}-E_{0})}}}$,

where ${\textstyle C_{1}}$ and ${\displaystyle E_{1}}$ are the cost and effect in the intervention group and where ${\textstyle C_{0}}$ and ${\textstyle E_{0}}$ are the cost and effect in the control care group. Costs are usually described in monetary units, while effects can be measured in terms of health status or another outcome of interest. A common application of the ICER is in cost-utility analysis, in which case the ICER is synonymous with the cost per quality-adjusted life year (QALY) gained.