You can download the 1-Wire Temperature Logger Calculator here.
This calculator can be used for the DS1921G, DS1921H, DS1921Z, DS1922E, DS1922L, DS1922T, DS1923 iButton data loggers.
You only need to enter your Mission settings and then the calculator's software GUI will give you the result of the expected time in minutes, hours, days, or years, based on the memory capacity of the specific device.
Keep in mind that both faster sample rates and ambient temperature affect the lifetime of the battery. Refer to the product data sheet to estimate the battery life expected based on the sample rate and temperature.
In the following example with the DS1921G, the sample rate is set to once every 120 minutes (every 2 hours). The calculator shows that in about 170 days the memory will be full.
This information will be useful in order to manage the effective lifetime of the iButton. If the rollover feature is disabled, the device will not write over the captured data once the memory is full. However, the device will continue sampling (and not storing the data) until the mission is disabled. Thus, any data sampled after the memory is full will be lost.
NOTE: This calculator only gives you the estimated samples that can be obtained for the data logger. The results may be affected by the status of the battery. If the missioned data logger has been used for several years, consult the product datasheets for infomation about battery life.