Threshold for COPD | Formula |

Fixed ratio | FEV_{1}/FVC <0.7 (GOLD stage 1 or higher) |

LLN (FEV_{1}/FVC) | FEV_{1}/FVC <5th percentile (predicted FEV_{1}/FVC minus 1.645×sd) |

GOLD stages 2–4 | FEV_{1}/FVC <0.7 and FEV_{1} <80% pred |

LLN (FEV_{1}/FVC) and FEV_{1} <80% pred | FEV_{1}/FVC <5th percentile and FEV_{1} <80% pred |

LLN (FEV_{1}/FVC) and LLN (FEV_{1}) | FEV_{1}/FVC <5th percentile and FEV_{1} <5th percentile |

LLN (FEV_{1}/FEV_{6}) and FEV_{1} <80% pred | FEV_{1}/FEV_{6} <5th percentile and FEV_{1} <80% pred |

For all but the fixed ratio, alternative versions may be computed based on choice of prediction equation. This table just describes general formulas. FEV

_{1}: forced expiratory volume in 1 s; FVC: forced vital capacity; GOLD: Global Initiative for Chronic Obstructive Lung Disease; LLN: lower limit of normal; % pred: % predicted; FEV_{6}: forced expiratory volume in 6 s.