Dog heat cycle predictor calculator

What this calculator does

Dog heat cycle predictor works out estimated stage dates and next heat window from the last cycle's start date. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.

The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.

The formula

The inputs explained

Worked examples

Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.

How the answer changes with average cycle interval

Every other input is held at the calculator’s starting values while average cycle interval varies. Select any row to load that scenario into the calculator.