Partition Alignment Calculator
Find the aligned start and size for a partition and the padding each boundary costs.
Stripe width against the 1 MiB convention
A stripe of chunk × data disks is often not a multiple of 1 MiB, so the alignment unit becomes the least common multiple of the two. These are the units for a few common layouts.
| Chunk | Data disks | Stripe width | Alignment unit |
|---|
Modern partitioning tools start the first partition at 1 MiB because that byte offset is a multiple of 512-byte and 4096-byte sectors, of every power-of-two RAID chunk and of the usual 4 KiB filesystem block, so the first write of the partition lands on a whole stripe. A start that is only sector-aligned still works, but on a drive with a larger physical sector (a 512e disk) the controller has to read-modify-write each partial block. Sizes are rounded up to the same unit so the next partition can start on a boundary too. MiB values accept up to six decimals and are converted to whole bytes; the tool never reads or writes a disk and everything is calculated in your browser.