This paper describes FPC, a lossless compression algorithm for linear streams of 64-bit floating-point data. FPC is designed to compress well while at the same time meeting the high throughput demands of scientific computing environments. On our thirteen datasets, it achieves a substantially higher average compression ratio than BZIP2, DFCM, FSD, GZIP, and PLMI. At comparable compression ratios, it compresses and decompresses 8 to 300 times faster than the other five algorithms.