Use FEV1/FVC Ratio when you need to compute the FEV1/FVC ratio from forced expiratory volume in one second and forced vital capacity in litres. Enter FEV1 and FVC using the definitions and units below so the result can be reproduced.

FEV1

A finite measured or assumed value greater than or equal to 0, expressed in L.

FVC

A finite measured or assumed value greater than or equal to 0, expressed in L.

The published tool contract uses this rule: Compute the FEV1/FVC ratio from forced expiratory volume in one second and forced vital capacity in litres.^[1]

FEV1/FVC ratio

The calculated fev1/fvc ratio.

A ratio or percentage can conceal the scale of its numerator and denominator and becomes sensitive to measurement error when the denominator is small.

Retain the original FEV1 and FVC values and their units alongside the result. a/A Ratio is useful when you instead need to compute the arterial-to-alveolar oxygen ratio as PaO2 divided by the alveolar oxygen tension from the simplified alveolar gas equation. V/Q Ratio provides another view by helping you compute the ventilation-perfusion ratio as alveolar ventilation divided by pulmonary blood flow.

• a/A Ratio

  Compute the arterial-to-alveolar oxygen ratio as PaO2 divided by the alveolar oxygen tension from the simplified alveolar gas equation.

• V/Q Ratio

  Compute the ventilation-perfusion ratio as alveolar ventilation divided by pulmonary blood flow.

• Dairy BCS Ratio Mapping

  Map a precomputed body-condition ratio onto a one-to-five score with round(ratio times five), clamped to the scale. This is a heuristic mapping, not a substitute for visual and palpation scoring.