Well, there is actually if you are using a power meter… at least, you should be able to get within a few percent which is far better than most other exercises. Very briefly and oversimplified, just look at your power output in kJ … that’s essentially your calorie burn.
There are several articles online that discuss why this is and I won’t belabor it, but if your device says you burned 1000 calories and you only put out 500kj total for example, something is very wrong. With a 500kj output, the calorie range should be between 480-520, which is a pretty tight margin. On the lower side if in good shape, or higher side if not. Can there be exceptions? Sure…
Naturally this assumes you have an accurate power meter, which is often not the case. A HR meter can help hone this in. Live example: just did a ride where I output 875kj. I’m in pretty good cycling shape, so in looking at my calorie burn and HR data, zwift/Strava says 848 kcal. That checks out. About as close as you can get without true medical equipment.
I’m not a medical expert, but I’ve read a lot in my training to try get a better understanding. We are pretty fortunate in cycling to have some decent ways to reasonably gauge effort.