The Shulchan Arukh describes the measurement of the three steps back taken after amidah in OC 122:3 (translation my own):
וְשִׁעוּר פְּסִיעוֹת אֵלּוּ, לְכָל הַפָּחוֹת, הוּא כְּדֵי שֶׁיִּתֵּן גּוּדָל בְּצַד עָקֵב
And the size for each of these steps is at least enough so that the big toe is placed alongside the heel.
I have noticed that in the vast majority of shuls there is not sufficient space in the pews to take three steps back with the measurements described. What should one do if he finds himself in such a pew? I can think of three possible options but do not have sources to support option 2 or 3.
- Step out to a space where there is sufficient room
- Take steps directly back with smaller measurements
- Take steps on a diagonal so that the measurements are correct