The effects of idiopathic Parkinson’s disease (IPD) on speech include articulatory imprecision. We quantified articulation rate and range acoustically using cepstral coefficients to represent vocal tract settings. Cepstral coefficients were extracted from 10 sentences spoken by 76 talkers, half of which were diagnosed with IPD. Articulation range was estimated for each sentence as the sum across cepstral coefficients of the standard deviation of each coefficient, and articulation rate was estimated using the same procedure, replacing cepstral coefficients with delta coefficients. The mean ± standard deviation (N = 380 sentences) for the articulation measures of range (7.95 ± 0.50 vs. 6.66 ± 0.53) and rate (5.64 ± 0.56 vs. 4.40 ± 0.46) were significantly different (t-test, p < 0.001) for normal vs. IPD speech, respectively. In a leave-one-talker-out classification experiment, range accuracy was 90.1%, rate accuracy was 88.8%, and accuracy was 92.9% using a combined model of articulation range and rate. The strengths of the articulation measures include 1) sensitivity to IPD speech, 2) reliance on cepstral coefficients which have been used for over 30 years to represent speech, 3) no segmentation requirements, 4) low sensitivity to speech material, and 5) effective with only 2 seconds of speech.