Enter a start date, the number of weeks you have in total and the share of that span each block should take, and the table returns the weeks per block along with the date each block starts and ends. Up to four blocks are supported, and any block left at zero or blank drops out automatically. A total you worked out backwards from a competition date can go straight in.
Weeks are divided by the largest remainder method. Each share is multiplied by the total and rounded down, then the leftover weeks go one at a time to the blocks with the biggest remainders, so the block weeks always add back up to the total exactly. Dates are computed in milliseconds against universal time, so month ends and leap years stay correct, and each block begins the day after the previous one ends. As of October 2026 no authoritative standard for how many blocks to use or how to weight them is published, so the shares are inputs.
For that reason the page does not recommend a phase structure by sport, or say what to train inside each block. Blocks are simply labelled one through four. When the total is short and a share is small, a block can land on zero weeks, and the result says how many blocks that happened to.
Frequently Asked Questions
No authoritative standard is published. This tool recommends nothing and simply divides the weeks by the shares you type in.
No. After rounding down, leftover weeks go to the largest remainders, so the sum always matches the total you entered.
The calculation stops and reports the current total as a percentage. Fix the shares to 100% and the table appears.