Why the delay changes
Earth and Mars orbit the Sun at different speeds. At their closest, around an opposition, they can be under 60 million km apart and a signal takes about 3 minutes one way. When Mars is on the far side of the Sun the distance is around 400 million km and the delay exceeds 22 minutes. Near that point, the Sun can block communication altogether for about two weeks.
How the calculation works
one-way time (s) = distance (km) ÷ 299,792.458
Round trip is twice the one-way time. The distance for a date comes from Keplerian orbital elements published by NASA JPL for approximate planetary positions (valid 1800–2050), computed in your browser.
Example: at 100 million km a message takes 333.56 seconds one way and 667.13 seconds round trip.
What it means for daily life
A live video call is impossible. Families would trade recorded messages, more like letters than conversations, and crews would need to solve emergencies without waiting for instructions from Earth.
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