Seagate Skyhawk Surveillance 4TB Hard Drive Disk SATA III 3.5" HDD HD Harddisk For Security System Video Recorder DVR NVR CCTV

1TB = approximately 931GB 2TB = approximately 1.81TB 3TB = approximately 2.72TB 4TB = approximately 3.62TB This is calculation difference between manufacturer and your PC, please Google 'Memory card capacity' to get more information. Your PC says 1GB = 1.073741824 Billion bytes where Market Defines 1 GB = 1.00 Billion bytes.