A disk drive and method for estimating a sinusoidal error in a wedge time period is disclosed. An estimated WTP is calculated according to: EST_WTP=RTP+a*cos(2.pi.k/N)+{circumflex over (b)}*sin(2.pi.k/N) wherein RTP is a reference time period corresponding to a nominal WTP, k is an index representing a servo wedge, and {a,{circumflex over (b)}} are adjustable coefficients. A wedge time error e(k) is estimated as the difference between the estimated WTP and a detected actual WTP. The coefficients {a,{circumflex over (b)}} for generating the estimated WTP are adjusted according to: a(k+1)=a(k)-G*e(k)*cos(2.pi.k/N) {circumflex over (b)}(k+1)={circumflex over (b)}(k)-G*e(k)*sin(2.pi.k/N) wherein G is a predetermined gain.