Stellar standard candles provide the absolute calibration for measuring the Universe's local expansion rate, H0, which differs by ∼ 8% from the value inferred using the Cosmic Microwave Background assuming the concordance cosmological model, ΛCDM [1,2]. This Hubble tension indicates a need for important revisions of fundamental physics [3]. However, the accuracy of the H0 measurement based on classical Cepheids has been challenged by a measurement based on the Tip of the Red Giant Branch (TRGB) method [4]. A resolution of the Cepheids vs. TRGB dispute is needed to demonstrate well-understood systematics and to corroborate the need for new physics. Here, we present an unprecedented 1.39% absolute calibration of the TRGB distance scale based on small-amplitude red giant stars (OSARGs). Our results improve by 20% upon previous calibrations and are limited by the accuracy of the distance to the Large Magellanic Cloud. This precision gain is enabled by the realization that virtually all stars at the TRGB are variable -a fact not previously exploited for TRGB calibration. Using observations and extensive simulations, we demonstrate that OSARGs yield intrinsically precise and accurate TRGB measurements thanks to the shape of