  We present theoretical predictions for the production of top-quark pairs with
up to three jets at the next-to leading order in perturbative QCD. The relevant
calculations are performed with Sherpa and OpenLoops. To address the issue of
scale choices and related uncertainties in the presence of multiple scales, we
compare results obtained with the standard scale HT/2 at fixed order and the
MINLO procedure. Analyzing various cross sections and distributions for
tt+0,1,2,3 jets at the 13 TeV LHC we find a remarkable overall agreement
between fixed-order and MINLO results. The differences are typically below the
respective factor-two scale variations, suggesting that for all considered jet
multiplicities, missing higher-order effects should not exceed the ten percent
level.
