Breaking down your working week
You can analyze how much you might already be a manager, by breaking down your typical week to understand how much of what you do is pure software development versus anything else.
You could try putting anything that is not regarded as pure software development, or personal learning and development, into the "managerial" category. The goal here is to give you a rough idea of how much time you currently spend not doing software development, and how much time you already spend doing management-related tasks.
The answers you get might just surprise you. One tried and tested way to analyze your time is with the Time Log method devised by Peter Drucker in his ground-breaking book, The Effective Executive. You can break down your working time into 15-minute units, and you classify them into a particular purpose or category, such as coding and managerial. You may be pleasantly surprised at how much managerial work you already do, and even enjoy!
To make it even more scientific and discerning, you could make a simple side-by-side comparison between the average week of a manager you respect and your own week. Better still, speak with them to understand what their typical week looks and feels like. The idea is to gauge how much overlap there is between you as a developer, and them as a manager.