Ra-223 is an alpha-emitter that is being used as a bone-seeking radiotherapeutic agent. The relatively large uncertainty on its half-life (0.26 %, Bé et al., 2011) is an impediment to precision activity assays. We have performed two series of measurements using an ionization chamber (IC) and a NaI(Tl) well counter (γ-wc) to determine new, precise values for the 223Ra half-life. We have endeavored to realistically assess the uncertainties on the derived half-lives, looking beyond the fit uncertainties to identify uncertainty components acting on multiple timescales. We recovered respective values of 11.447(6) d and 11.445(13) d from the IC and γ-wc measurements.