I’ve been through this already. Not just simple math.
In supercruise fuel is burned at a constant rate. Full throttle, half throttle, closed throttle is all the same number. This is the simple part.
Speed, however, depends on throttle setting and your proximity to a gravity well, such as a star or a planet. Funny thing about the frame shift drive is it’s counter intuitive to normal Newtonian mechanics. The frame shift decelerates heading toward a massive body and accelerates heading away from same. Gravity apparently affects its ability to shift your position in space with higher gravity bogging it down.
When you head out from the system entry point sun toward that far remote station, your acceleration gradually increases as you move away from and out of the star’s gravity. Your speed peaks at 2001c or whatever speed you attaine before you enter the gravity influence of the planet the destination station is orbiting. At that point the frame shift drive starts bogging down again and your speed starts dropping as you approach the destination. Math wise for the simplest case, we have an initial varying acceleration to max speed, a possible constant speed leg, then varying deceleration to the destination. And that’s only if there are no other massive bodies between you and your destination, which only further complicates the situation. So not simple math. And, regretfully, not an answer to your question.
Fortunately, in the game this is rarely an issue. But there are strategies to minimize fuel burn when heading to the distant edges of a system. Use a route that arcs above the systems orbital plane. In general, all a systems planets orbit in the same plane, so flying an arc above the orbital plane allows most of the flight to occur in free space clear of any of the other planets gravity influence. This allows the frame shift to best achieve and sustain maximum velocity. You end up flying farther, but at a much higher average speed resulting in a shorter flight and thus less fuel burned.
