The TwinThink locker calculator starts from one rule: one person, one compartment. If people work in shifts, it counts only the largest shift, because shifts share lockers.
The model depends on what each person stores. A coat or uniform kept unfolded needs a full-height compartment, the one in the 2-door locker. A backpack, bag and jacket fit the 82 cm compartment of the 4-door locker. A helmet, a charger or small items go in the 41 cm compartment of the 12-door locker.
From there it works out how many lockers of that model you need and how much wall they take: 65 cm wide for the 2 and 4-door models and 97 cm for the 12-door, all 40 cm deep. If you enter the wall width you have and they do not fit, it suggests a model with more compartments per metre. When you send the list to the quote form, the lockers are added in grey; you can change the colour and quantity afterwards.