Within the context of International Humanitarian Law (IHL), proportionality is a moderating principle that seeks to constrain the use of force. The principle was formally codified in 1977 in Protocol I of the Geneva Conventions. The protocol prohibits “an attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated.” Proportionality is thus not about clear lines of prohibition, but rather about calculating and determining balances and degrees. Although violence is in constant need of measurement, the principle of proportionality provides no scale, no formulas, and no numerical thresholds. Instead, it demands assessment on a case-by-case basis, within parameters that are always relative and immanent. By opening a field of equivalence in which different forms of potential and actual violence, risk, and damage become exchangeable, proportionality approximates an algorithmic logic of computation—although, still, in practice, it is rarely computed.