VDOT is the performance index coach Jack Daniels uses in Daniels Running Formula: one race result maps to a single number, described as pseudo VO2max, that captures aerobic capacity and running economy together. The published tables span roughly VDOT 30 to 85, and the number exists to set training paces, not to grade you.
No. VO2 max is oxygen uptake measured in a lab. VDOT is derived from what you actually raced, so running economy is baked in: two runners with the same lab VO2 max can hold different VDOTs, and watch-estimated VO2 max typically reads higher than a race-derived VDOT.
Daniels defines easy running at 59 to 74 percent of VO2max, a conversational effort. This calculator shows the zone as a pace range calibrated to the published Daniels tables, and both ends count: most of your weekly volume belongs inside that range, not below it.
In the Daniels system they are the same intensity. Threshold sits at 83 to 88 percent of VO2max, comfortably hard, and a classic tempo run is about 20 minutes of steady running at that pace. If you cannot get a sentence out, you are above threshold.
Your most recent all-out race, ideally from the past 4 to 6 weeks, which is the guidance VDOT O2 gives for its own calculator. A 5K or 10K works best for most runners. Never enter a goal time: every training pace inherits the optimism in the input.
Each Marathon Ballot tool does one job. Equivalent race performances across distances are handled by the race time predictor, and the qualification checker scores a marathon time against all eight Abbott World Marathon Majors. This page keeps to the five Daniels training paces.