Background Metacarpal fractures are common and can often be managed non-operatively with excellent outcomes. Shortening, angulation or displacement of the fracture can be indications for operative management. Biomechanical studies examining the effects of metacarpal shortening on extensor lag, pinch strength and intrinsic muscle function have shown significant detrimental effects at roughly 5mm of shortening. Estimations of shortening in a clinical setting are made from plain film Xrays and current methods significantly overestimate the degree of shortening. We aim to describe the relative lengths of metacarpals measured on Xray and use this to more accurately calculate shortening in a fractured metacarpal. Methods 200 plain film AP Xrays of the hand performed for the purpose of ruling out injury were analysed and the lengths of the 2nd to 5th metacarpals measured. Xrays were stratified by sex, age and laterality, and only patients aged 18 and above were included. Metacarpal lengths were examined to assess their relationships to eachother Results The lengths of the second to 5th metacarpals were 69.2mm, 67.03mm, 59.6mm and 54.8mm respectively. The 5th MC was on average 0.78x the length of the 2nd metacarpal. Conclusion We have described the lengths and relative lengths of the 2nd to 5th metacarpals. This data can be used in the future to assist with translation of biomechanical studies into clinical practice, and assist in clinical decision making.