I'm new to dance and have a couple questions about music. I see that dances have tempo such as 30 mpm and I would understand bpm but what does mpm stand for? Also is there an easy way to understand how to start on the one?
Thank you

As a man in the Waltz take a preparation step with the left foot on three , then step onto the first beat of the bar on one . Foxtrot prepare on three four, walk in on, one two, with the music of course. Hope this doesn't confuse

Hi misterb
mpm (measures per minute) and bpm (bars per minute) are the same thing. A 'measure' is simply another word for a 'bar' of music.
In waltz, a bar of music contains 3 beats, and competition tempo for slow waltz is 30bpm.
How to recognise beat 1 of the bar(in any music, not just waltz) is a skill which must be developed. Normally, beat 1 is emphasized. Often there is a low note, or a drum beat on beat 1 - but not always!!
Start with some simple music, where beat 1 will be much easier to identify, and start with waltz music because this is usually the simplest. Count out the beats aloud and tap your hand on these beats. Emphasize beat 1 strongly with your tapping. Eventually, it will become natural. Foxtrot and quickstep have 4 beats in the bar, and beat 1 is again usually the most emphasised, though beat 3 is often also strong. It's not easy!! but you will develop the skill - you're not alone in having this problem. Those who play a muscial instrument have a huge advantage.
As 'quickstep' has pointed out, dancers usually start with a preparatory step or two on beats 3, or 4 as appropriate. But the main task is to identify beat 1.

Phil is quite correct, however there is one potential problem. There are two possible interpretations of the term bpm.

Ballroom dancers usually think of "bars" per minute as Phil did. Most musicians and club DJs however think of "beats" per minute. Their tempii are thus typically 3 or 4 times those used by dancers, eg a waltz would be 90 or a foxtrot would be around 120.

The use of the term mpm helps to avoid this confusion.

I agree absolutely with the comments above from the two writers. I will pass on what I used to do. I would put a record on ,they were records in those days. With a paper and pencil on hand I would count every beat, putting a tick down for every bar that I counted all the way through after the four bar introduction right to the end. At first it wasn't uncommon for me to get a different count on the same record. I soon figured out that well into the recording my consentration would wane. I still do this counting today,and have no trouble with the timing whether it be a Rumba or Foxtrot. I also like to count in eight bar sequences, Like 123.223 323 423 up to eight bars in the Modern Waltz and through to the end. A little bit of sound advice her. Let the introduction go past if you are on the competition floor especially in Latin. I've know the beats to alter after the intro. and found I was on the wrong beat. In Paso of course you have no choice but to take off on the first beat, no intro there.

You're right socialdancer. Bands use the beats-per-minute on their keyboards.
If you want to measure the B(ars)PM, count the beats for 20 secs in watltz and 15 seconds in quickstep/foxtrot.
Picking beat 1 is the biggest problem, especially when you're under pressure in a comp. I find i have to focus on picking the beat instantly the music starts in a comp, but socially, it happens without thinking.