The friction-vs-quality tradeoff
HubSpot's analysis of 40,000 landing pages found conversion rate dropped from 13% (3 fields) to 5% (6 fields). The straightforward conclusion: fewer fields = more conversions. The hidden caveat: if you're collecting bad leads, "more conversions" makes downstream work worse, not better. Pure volume optimization kills sales-team productivity.
The rule that beats both extremes
Ask only what you need to act on the lead in the next 24 hours. For an email newsletter, that's email. For a sales call, that's name, email, company, role. Don't ask for "company size" or "budget" until your sales team actually uses them in qualification — most don't, and you're costing yourself conversions for data nobody opens.
Multi-step beats long single-page
A 7-field form split across 3 steps converts better than a 7-field single page. The first step (1–2 easy questions) has high completion; once started, sunk-cost commitment carries visitors through the rest. Audit your form for fields you can drop or postpone.