The main challenge to modelling ab-initio electrochemical barriers in periodic simulation cells of feasible size is that the workfunction (often used as an alias for the electrode potential) changes by about 1-2 eV during the course of a reaction involving an ion-electron pair or adsorption of a polar intermediate. This change is an artifact of the finite nature of a super cell, containing a fixed number of electrons. At the hypothetical infinitely sized cell there would be no change in the workfunction accompanying a reaction, guaranteeing that the simulated electrochemical reaction proceeds without a change in the potential. In the past decade, a variety of methods to address this challenge have been developed. These methods can be broadly grouped into two categories, extrapolation and grand-canonical schemes. Extrapolation methods seek to determine activation energies at the limit of infinite cell size by correcting DFT energies for finite cell size effects. For example, in Ref 11, 12 the infinite cell limit is reached by extrapolating energies from DFT calculations done at successively larger cell sizes, through so-called cell extrapolation. Another approach is to a priori assume that the electrochemical interface can be modelled as a parallel plate capacitor, where the periodically repeated ion (or adsorbate) forms one end and the metal surface the other. The charge stored in the parallel plate capacitor is determined through a charge partitioning approach and the potential is estimated through the workfunction. In this "charge extrapolation" scheme the DFT energies are corrected with a purely electrostatic model, to obtain energies at the infinite cell size, assuming a linear change in potential with the amount of charge on the capacitor plates. Alternatively, grand-canonical (GC) methods keep the workfunction constant by adding or subtracting excess electrons within the simulation cell, along with a corresponding countercharge in different possible continuum models of the electrolyte. Recently, a class of methods have attempted to combine the two approaches, i.e. performing DFT calculations which change the workfunction by adding or subtracting excess electrons while using the capacitor equations to interpret the obtained energies. In theory, it has been shown that both GC and extrapolation methodologies are equivalent in specific limiting cases, such as adsorption reactions of polar species. For example, Ref 17 showed that for CO 2 → CO * 2 both GC and extrapolation procedures provide the same potential dependent energies. However, in practice, challenges still remain. Cell extrap-olation is computationally demanding, while charge extrapolation necessitates charge partitioning, which has short-comings in cases of strong hybridisation between atoms. For example, charge transferred along the reaction path for protonation to oxygen and nitrogen intermediates show sharp changes, inconsistent with a capacitor treatment. This behaviour is likely a failure of charge partitioning as a consequence of increasing hybridisation between the reacting species. Furthermore, rotation of water along a reaction path leads to abrupt changes in the workfunction. Grand-canonical methods require an accurate capacitance in order to avoid cell-size dependence of reaction energetics. Finally, all of the above methods are typically applied with static water structures, while dynamic simulations under constant potential are only recently emerging. In this work, we propose a method to determine potential dependent energetics of electrochemical reactions by building upon the framework of extrapolation methodologies. The strength of our approach is that we determine the charge transfer coefficient directly from atomic positions and atom centered forces, without the need for explicit partitioning of the charge density or performing multiple DFT calculations. We begin by illustrating the current extrapolation based procedure to determine charge transfer coefficients and potential dependent energies for a prototype reaction of a proton-electron transfer to C adsorbed on Pt(111). We then develop a model which relates the atom centered forces to the charge transfer coefficient. The computational overhead associated with implementing our approach is equivalent to a typical finite difference Hessian calculation. We show that the force-based method is able to provide consistent charge transfer coefficients for a range of reactions, irrespective of how strongly the reacting species are hybridised. We benchmark this methodology against calculations done at different cell sizes, i.e. through cell extrapolation and discuss possible limitations.