We use measurements from NASA's Van Allen Probes to calculate the decay time constants for electrons over a wide range of energies (30 keV to 4 MeV) and L values ( L = 1.3–6.0) in the Earth's radiation belts. Using an automated routine to identify flux decay events, we construct a large database of lifetimes for near‐equatorially mirroring electrons over a 5‐year interval. We provide the first accurate estimates of the long decay timescales in the inner zone ( ∼100 days), which are highly resolved in energy and free from proton contamination. In the slot region and outer zone, we compare our lifetime calculations with prior empirical estimates and find good quantitative agreement (lifetimes ∼1–20 days). The comparisons suggest that some prior estimates may overestimate electron lifetimes between L≈ 2.5–4.5 due to instrumental effects and/or background contamination. Previously reported two‐stage decays are explicitly demonstrated to be a consequence of using integral fluxes. Plain Language Summary The Earth is surrounded by two invisible, donut‐shaped belts of charged particle radiation (think electrons and protons) called the Van Allen belts. The particles in these belts orbit rapidly around the Earth in the same region where spacecraft fly, like GPS and weather satellites. Since the particles in the belts can damage satellites, we need to understand what specific processes make the intensity of the belts go up and down. Knowing which processes are important for changing the belt intensity helps us build better computer models that can be used to predict the future state of the belts (much like weather prediction models). This letter uses spacecraft observations to estimate the loss timescales in the radiation belt region, which are then used in a companion paper to better understand the processes that make the belt intensity go down. Key Points A large database of radiation belt electron decay timescales is calculated from Van Allen Probes MagEIS measurements We provide the first accurate estimates of these timescales over a wide range of energies in the inner zone, free from proton contamination Outer zone decay timescales generally agree well with prior estimates; some differences exist and may be due to instrumental effects