A new method to evaluate the dust-to-gas ratios in the Kepler SNR is presented .
Dust emission in the infrared and bremsstrahlung are calculated consistently , considering that dust grains are collisionally heated by the gas throughout the front and downstream of both the expanding and the reverse shocks .
The calculated continuum SED is constrained by the observational data .
The dust-to-gas ratios are determined by the ratio of the dust emission bump and bremsstrahlung in the infrared .
The shell-like morphological similarity of X-ray and radio emission , and of the \Ha and infrared images confirms that both radio and X-ray emissions are created at the front of the expanding shock and that dust and gas are coupled crossing the expanding and reverse shock fronts .
The results show that large grains with radius of \sim 1 \mum with dust-to-gas ratios < 4 10 ^ { -3 } 
survive sputtering and are heated to a maximum temperature of 125 K downstream of the shock expanding outwards with velocity of about 1000 \kms .
The high velocity shocks become radiative for dust-to-gas ratios > 10 ^ { -3 } .
Such shocks do not appear in the NE region , indicating that dust grains are not homogeneously distributed throughout the remnant .
Smaller grains with radius of about 0.2 \mum and dust-to-gas ratios of \sim 4 10 ^ { -4 } are heated to a maximum temperature of \sim 50 K downstream of the reverse shock corresponding to velocities of about 50 \kms .
A maximum dust mass < 0.16 \msol is calculated .