Provided are a computer program product, system and method for determining adjustments to the spare space in a storage device unavailable to a user based on a current consumption profile of a storage device. A current write amplification is based on storage writes to a media at a storage device and host writes from a host to the storage device. An adjustment to the current write amplification is determined to produce an adjusted write amplification based on an estimated lifespan of the storage device, a maximum storage writes for the storage device, and the storage writes at the storage device since the storage device was powered-on. A determination is made to an adjustment to spare space based on the adjusted write amplification. The spare space and the free space available to the user are reconfigured to adjust the spare space by the determined adjustment to the spare space.