In this paper, we propose an efficient fixed-point IMDCT algorithm for high-resolution audio (or audio/video) appliances such as digital media receiver (DMR) and high-end portable media player (PMP). A novel block floating-point algorithm and a method of reducing the number of guard bits are proposed to implement IMDCT. The former can compute IFFT-based IMDCT with same efficiency as higher radix IFFT and has same number of guard bits as radix-2 IFFT. The latter can reduce the number of guard bits based statistical bit growth pattern. Experimental results using high-resolution advanced audio coding (AAC) decoder show that the 32-bit IMDCT implemented by the proposed algorithm can comply with a 24-bit AAC decoder with 20% ~ 50% less computational complexity when compared with existing 48-bit IMDCT. The proposed algorithm can be used efficiently for low-complexity implementation of high-resolution audio appliances.