Most people recommend 4 ft or less width for weeding purposes.
I don't know how old you are, or the status of your back, but I would go with 3' wide if any of the above are a concern to you in the near future!
My asparagus bed is 4' wide and I have troubles getting to the weeds in the center without stepping into the bed.
All my other beds except one are 3 ft wide and I have no problem with them. The other 4' bed isn't a perennial bed, so it gets covered in the winter and fluffed up in the fall, so very few weeds.
With the 3' beds, you would probably need more path room for the plants to expand so you don't trip over them (which happens occasionally anyway!)
Good thing to think ahead! I started with an 8x8 bed (now converted to 2 3x8s with a tiny 1 ft path down the middle!)
Had I been reading these forums in advance, I would have planned my garden much differently!
All in all, it's turned out quite nice, thank you very much! ;) Nancy

As far as the plants, No known garden veggie requires 4 ft. But for the width of bed, 4ft is ergonomically is good number. You can reach it by walking around it (2 ft arm length). and you can plant 2 rows of just about anything.

My squash and potato beds are 12X12. I have to step in, but only a few times a year. They are all one harvest crops and are bugs free (if you use moschata squash).

but the depth is the problem.

Do you mean width rather than depth? Width I recommend is like Nancy said 4 feet if you have access to both sides and plan to plant close to the side walls. Otherwise it can be wasted space. Otherwise 3' can be ideal for most crops..

Depth is another issue. Many recommend 12" but I find 18" to be much more effective- especially for corn and potatoes.

Dave

My potato and corn beds are 4' x 16' and 12' deep. I grow my squash up the corn stalks.

I've started a 4x4x4 potato grow box this year and am anxious to see how it compares to the regular row crop of potatoes. I already have sprouts so that's a good start.

As for reaching the middle of the beds I made a seat that basically slides onto the edge of the bed so I can sit or kneel if I need to. Very simple design made from left over lumber and I can move it anywhere.

Here is a link that might be useful: Raised Bed Seat

Thank you, yes, I meant width (there are hazards to posting too late at night). I will go with 4 feet, as I prefer not to have overhang of the pumpkins. Overhang means it is difficult to see if there are snakes hiding, I like my paths to be rather clear. I am on the taller side and my back is fine so reaching in the 4 feet is not much of a problem (knees are harder for me but no matter the width, I will have to bend down when not using a hoe for weeding). All beds will be double dug at least 18 inches, I hate going to plant and hitting the hardware cloth. Thank you for all input.

You can train the pumpkin vines to stay in a three foot wide bed. Every day just move the very end of any vine that is starting to hang over.

But there is nothing wrong with 4 foot beds either. Mine are all 4 feet by 8 feet.

McKenzie