This is a fun topic to discuss. I remember being floored when I first joined BCG and saw the salary bands presented internally!
Quick answer: between $500K - $5M. The fun part though is in the details that drive that variance. Let's look at the three big factors that drive that variance:
While everyone generally just says "Partner" all of these firms have multiple tiers of Partners and these types tend to have different fixed, base salaries. There are junior partners and senior partners.
For example, at BCG there are junior partners referred to just as "Partner" and then senior partners called "Partner and Managing Director." At Bain, they have a similar tiering: junior partners are called "Operational VPs" and senior partners are "Directors."
Every firm has a different way of calculating partner compensation, so it can vary but they all generally look at the same drivers:
Cases sold: what business did you bring in? For all the firms this matters a lot, although none of the elite firms do a direct commission off cases sold, likely because they don't want to directly incentivize "pushy" sales behavior.
Company performance: how is the business performing overall? Great year? OK year? Bad year? This one is pretty straight forward and makes sense after all, you are a Partner in a Partnership, so overall performance will matter.
Case collaboration: This is an interesting one and the firms all have various ways of rewarding Partners for collaborating with each other on cases. Anecdotally from what I've heard, Bain, true to their rep as the most collegial, goes the furthest in rewarding this.
Firm / office contributions: How much work are you doing to build the firm itself, further its brand (eg research, press, conferences), drive recruiting (eg run West coast recruiting), etc.
When you put all this together, you get a range of $150K - $5M for bonuses, a huge range! Also, it's worth calling out that the specifics of these formulas are closely guarded at every firm. While it's not difficult to consider what variables go in, how they're weighted, adjusted, etc is a trade secret. A good friend of mine who spent 8 years at Bain said "honestly, partner compensation feels like a black box for most of the partners!"
What do I mean by this? Specifically, which practice the partner is within (eg PE due diligence, implementation, pure strategy, digital, HR / change management). Currently, at MBB this isn't a big issue but that will change in the next 5 years as the firms expand the type of work they do (wrote on that in detail here).
For example, in the future, you could imagine the base salary and bonus formula for an implementation partner or digital labs partner to be different than pure "strategy." Within Bain, given their strong PE due diligence practice, a little of this has already emerged: partners there can co-invest with PE firms (this is possible with Bain Cap but also other PE firms they work with).
Ok, now, let's put it all together. From a compensation perspective, it's a pretty nice picture and now you'll understand why all these firms are flooded with resumes!
Looking at the final numbers, I'm guessing you'll agree with my initial reaction when I joined BCG: whoa! I've written a lot about the consulting career path and for anyone interested in what the salary and responsibility ladder looks like you can see that here.
Finally, it's worth noting that the senior partner range isn't evenly distributed. Most of those senior partners are likely pulling in around $1M - $2M annually, while the top 15% all-stars are making more than that.