The force that acts against you riding into the wind is proportional to the square of the relative wind velocity. If you are going into a 10 mph wind at 10 mph, the force is K*(10+10)^2 = 400 * K. If you are going 20 mph into a 10 mph wind, the force is K * (10+20) ^ 2 = 900 * K

The multiplier K depends on your frontal area and how aerodynamic you and your bike are, and the viscosity of the fluid you are moving through. It's harder to bike through water.