Calls a week. Your mobile carrier's app or your business phone portal lists every incoming call with a date and time. Count one normal week, not the week after a storm or a holiday.
Calls you miss. In the same log, count the calls marked missed, plus the ones that went to voicemail. Look closely at evenings and weekends: those are usually the hours nobody is at the desk.
Callers who would have hired you. Listen to a week of voicemails and sort them: real jobs, existing customers, sales calls, wrong numbers. The share of real jobs is a better number than a rule of thumb. Remember that many people hang up without leaving a message, so voicemails undercount.
What a job is worth. Use your average invoice for the kind of work that usually comes in by phone, not your biggest job of the year.
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