There's no universal slide count that makes a presentation good. But there is a consistent pattern in the ones that work, and it has almost nothing to do with the number on the deck.
The most common mistake isn't too few slides, it's too much on each one. A slide crowded with six bullet points, a chart, and a footnote forces the room to choose between reading and listening, and most people default to reading, which means your voice becomes background noise to your own presentation. The fix isn't necessarily more slides, it's less per slide, with one clear idea each.
If a slide can be understood with the sound off, it's doing its job. If it needs your narration to make sense, it's a script, not a slide.
A useful test while building a deck: could someone flip through it with no audio and still follow the argument? If yes, each slide is carrying its own idea clearly. If the slides only make sense with you talking over them, you've built a set of speaker notes disguised as visuals, and the audience will spend the whole time trying to read ahead of you.
Crowded: a slide titled "Q3 Results" with six bullet points covering revenue, churn, headcount, NPS, pipeline, and next steps.
Clear: five slides, each with one number and one sentence, "Revenue: $2.1M, up 8% from Q2" as its own slide, followed by "Churn: down to 4%, driven by the new onboarding flow" as the next.
On slide count specifically: there's no fixed right answer, but a rough guide is one slide per distinct idea, not one slide per topic area. A ten-minute presentation with fifteen single-idea slides moves faster and lands better than the same ten minutes spent on five overloaded ones, because the audience is never asked to hold more than one thought at a time.
Design polish matters less than people assume, and content clarity matters more than people assume. A visually plain deck with one clean idea per slide will outperform a beautifully designed deck that's cramming three ideas onto each page, because the audience's attention is a limited resource, and every excess element on a slide is competing with the point you actually want them to remember.
Last thing worth building into every deck: a genuine point of view. The presentations people remember aren't the ones with the most polished slides, they're the ones that clearly argue for something, rather than just presenting information and letting the room draw its own conclusions. If your deck could be read by two different people and used to support two different decisions, it's not done yet.