Why 'fewer fields' is the wrong default
The widely cited studies showing that removing fields lifts conversion are measuring submissions, not customers. Those are different metrics and they frequently move in opposite directions.
Remove the budget field and submissions rise. So does the share of enquiries from people who were never going to buy. If your sales team's time is finite — and it is — a higher submission count with a lower qualification rate can be a net loss.
What actually decides the number
- Cost of a wasted sales conversation. High cost justifies more qualifying fields. A self-serve product with no sales call justifies almost none.
- Whether the field genuinely changes what happens next. If nobody reads the answer or routes on it, delete it — that is not friction with a purpose, it is just friction.
- How motivated the visitor is at that moment. Someone arriving from a comparison search will tolerate more than someone who clicked a display ad.
- Whether you can infer it instead. Company size, industry and location can often be derived from an email domain without asking.
The test most people run wrong
A/B testing form length against submission rate will nearly always favour the shorter form, which is why the shorter form keeps winning. Test against qualified opportunities instead, and accept that this takes longer because the sample is smaller and the feedback loop runs at sales-cycle speed.
If you cannot wait that long, the fallback is to instrument both: track submissions and the downstream disposition of each one. A form that submits 40% less but converts 3× better on qualified pipeline is the better form, and only the second number tells you.