The confinement properties of future magnetic fusion devices can be extrapolated from existing experiments using the scaling of heat transport with relative gyroradius ( rho *). For H mode confinement regimes, this extrapolation to smaller rho * is complicated by the requirement that the loss power from core transport remain above the H mode threshold power. If the increase in H mode threshold power is more rapid than the increase in loss power when rho * becomes smaller, then the H mode threshold determines the scaling of global confinement for large devices rather than core transport. This can be avoided by choosing a scaling path at higher beta along which the loss power remains above the H mode threshold power to the point of ignition. The parameters for an ignition tokamak plasma that take full advantage of the gyro-Bohm-like scaling of heat transport in H mode plasmas are presented