Measurements of charm mixing parameters from the decay-time-dependent ratio of to rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding <?format ?>to of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass <?format ?>energies recorded by the LHCb experiment. In the limit of charge-parity ( ) symmetry, the mixing parameters are determined to be , , and . Allowing for violation, the measurement is performed separately for and mesons yielding , for the direct -violating asymmetry, and at the 68.3% confidence level, for the parameter describing violation in mixing. This is the <?format ?>most precise determination of these parameters from a single experiment and shows no evidence for <?format ?> violation.