Meter without the filter, enter that shutter speed and the strength of your filter (in stops or as ND8, ND64, ND1000 …). Start the timer for long exposures in bulb mode.
Every stop doubles the time: new time = time × 2^stops. A 10-stop filter (ND1000) turns 1/60 s into 17 seconds.
Strong filters often add a colour cast and the metering gets less exact: check the histogram after the first frame.
Change one setting and see what the others must do: equivalent exposures and the EV.
Golden & blue hourSunrise, sunset, golden and blue hour for any place and day, with the sun's path.
Stars without trails (NPF)The longest exposure for pin-sharp stars, by the NPF rule and the old 500 rule.
Flash guide numberGuide number, distance or aperture for your flash, with ISO and partial power.