Measurements of charm mixing parameters from the decay-time-dependent ratio of D-0 -> K+ pi(-) to D-0 -> K-pi(+) rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding to 3 fb(-1) of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass energies recorded by the LHCb experiment. In the limit of charge-parity (CP) symmetry, the mixing parameters are determined to be x('2) = (5.5 +/- 4.9) x 10(-5), y' = (4.8 +/- 1.0) x 10(-3), and R-D = (3.568 +/- 0.066) x 10(-3). Allowing for CP violation, the measurement is performed separately for D-0 and (D) over bar (0) mesons yielding A(D) = (-0.7 +/- 1.9)%, for the direct CP-violating asymmetry, and 0.75 < vertical bar q/p vertical bar<1.24 at the 68.3% confidence level, for the parameter describing CP violation in mixing. This is the most precise determination of these parameters from a single experiment and shows no evidence for CP violation.