Method for determining the dimensions of an electrochemical cell, which method is implemented by a computer and allows a total area (S t) of the electrochemical cell to be minimized while maximizing an electrical signal generated by the electrochemical cell in operation, the electrochemical cell comprising: ∘ a membrane electrode assembly formed from two electrodes (12, 13) separated from each other by an electrolytic membrane, and two holding plates between which the membrane electrode assembly is in contact; ∘ the total area (St) of the electrochemical cell being defined in a plane parallel to the plane of the electrolytic membrane by: • an active zone (Za) of elongate shape having an aspect ratio defined by a length (L a) and a width (l a), the length (L a) being larger than the width (l a), in which zone each holding plate is liable to be deformed in a direction opposite to the plane of the electrolytic membrane, and by • a fastening zone (Zf) encircling the active zone (Za), in which zone each holding plate is fastened to the membrane electrode assembly; the method comprising the following steps: a. determining a first cost function expressing the variation in a first parameter (S̃ t) representative of the total area (S t) as a function of an adjustment variable (R̃ f) representative of said aspect ratio of the active zone (Za); b. determining, from a predetermined physical model of the electrochemical cell implemented in the computer, a second cost function expressing the variation in a second parameter ( P̃ U) representative of the generated electrical signal as a function of the adjustment variable (R̃ f); c. determining a so-called compound cost function (C c; C v) from the first and second cost functions (F, G) and identifying a value ((R̃ f) opt) of the adjustment variable (R̃ f) that optimizes the compound cost function (C c; C v) and that therefore conjointly optimizes the first and second cost functions (F, G). ∘ a membrane electrode assembly formed from two electrodes (12, 13) separated from each other by an electrolytic membrane, and two holding plates between which the membrane electrode assembly is in contact; ∘ the total area (St) of the electrochemical cell being defined in a plane parallel to the plane of the electrolytic membrane by: • an active zone (Za) of elongate shape having an aspect ratio defined by a length (L a) and a width (l a), the length (L a) being larger than the width (l a), in which zone each holding plate is liable to be deformed in a direction opposite to the plane of the electrolytic membrane, and by • a fastening zone (Zf) encircling the active zone (Za), in which zone each holding plate is fastened to the membrane electrode assembly; • an active zone (Za) of elongate shape having an aspect ratio defined by a length (L a) and a width (l a), the length (L a) being larger than the width (l a), in which zone each holding plate is liable to be deformed in a direction opposite to the plane of the electrolytic membrane, and by • a fastening zone (Zf) encircling the active zone (Za), in which zone each holding plate is fastened to the membrane electrode assembly; a. determining a first cost function expressing the variation in a first parameter (S̃ t) representative of the total area (S t) as a function of an adjustment variable (R̃ f) representative of said aspect ratio of the active zone (Za); b. determining, from a predetermined physical model of the electrochemical cell implemented in the computer, a second cost function expressing the variation in a second parameter ( P̃ U) representative of the generated electrical signal as a function of the adjustment variable (R̃ f); c. determining a so-called compound cost function (C c; C v) from the first and second cost functions (F, G) and identifying a value ((R̃ f) opt) of the adjustment variable (R̃ f) that optimizes the compound cost function (C c; C v) and that therefore conjointly optimizes the first and second cost functions (F, G).