The MOLLER experiment, which will measure parity‑violating asymmetry in electron–electron scattering, now has a complete theoretical description of all two‑loop electroweak terms. These corrections shift the electron weak charge by 1.5 % and add a residual uncertainty of 0.04 × 10⁻³, only four % of MOLLER’s target precision of 2.4 %. The calculation involved generating 6,264 two‑loop diagrams, reducing them with symbolic tools and expanding them in hard‑ and soft‑momentum regions. Checks on infrared poles and gauge invariance confirmed the result.

Previously, comparisons with older calculations (Refs. 49 and 50) showed differences at the level of a few × 10⁻³ in the weak charge, i.e. only a few % of the planned experimental accuracy. The present result therefore is consistent with earlier work to within the MOLLER uncertainty budget.

The dominant limitation now comes from hadronic vacuum polarization at one loop: values derived from e⁺e⁻ data versus lattice QCD differ by 0.6 %. This tension is about a quarter of MOLLER’s overall goal and represents the largest theoretical uncertainty in the prediction.

These findings provide the necessary precision input for MOLLER’s upcoming measurements and help refine the Standard Model prediction for the electron’s weak interaction strength.