Step 3. Use the equation of the calibration curve to adjust measurements taken on samples with unknown values. Substitute the measured value as x into the equation and solve for y (the true value). In the example from step 2, y = 1.05x + 0.2. Thus, a measured value of 75.0, for example, would adjust to y = 1.05(75) + 0.2 = 78.9.