A blended rate averages a mixed-seniority team into a single number: blended rate = total billed amount ÷ total billed hours. A month with 100 senior hours at $60 and 100 junior hours at $30 bills $9,000 over 200 hours — a $45 blend.
Why teams quote blends: the client sees one simple number, invoices are easier to read, and staffing gains a degree of freedom — people can be swapped without renegotiating a rate card.
Why blends bite: the number was priced against an assumed mix. Quote $45 on a 50/50 senior/junior plan, let delivery drift to 70% senior, and the same $45 now sells senior hours below their cost-plus price — margin erodes with the contract technically untouched. The mirror mistake is padding the blend for safety and losing the deal to a competitor who priced the real mix.
Working rules: recompute the actual blend monthly (billed amount ÷ billed hours, per project), compare it against the mix the price assumed, and treat a persistent gap as a repricing or restaffing conversation. The same averaging idea appears on the cost side — a blended monthly cost per employee — wherever per-person data is missing.
In Helia, the blend stays inspectable — every invoice line carries its own hours and rate, so invoice total ÷ hours is the de-facto blended rate for the month; on the cost side, profitability uses a blended average monthly cost per employee as the explicit fallback for anyone without a compensation record.