Boomerang found that emails written at Grade 3-7 get the highest response rates. Most professionals write at Grade 12+ — overly formal, padded, hedged. Aim for Grade 7-10 for clear professional emails that get replies.
Boomerang's analysis of 40M emails found Grade 3-7 had the highest response rates. Aim for Grade 7-10 for professional emails that still feel polished. Anything above Grade 12 typically means you're padding, hedging, or showing off vocabulary.
Yes — slightly. Sales/cold-outreach emails benefit from Grade 5-7 (very short, very direct) because the reader has zero context. Internal emails to colleagues can sit at Grade 9-10 because the context is shared.
Subject lines are too short for the standard formulas to compute reliably. Apply common sense: 4-7 words, action-oriented, no jargon. The Flesch-Kincaid formula needs ~30+ words to produce stable scores.
Usually no — that's the goal. Most professionals write too formally. Grade 7 reads as confident and clear, not casual. If you want to dial up formality, lengthen sentences slightly and replace contractions with full forms — that adds 1-2 grade levels without adding padding.
They typically score Grade 11-13 — slightly higher than ideal, with consistent sentence length and overly formal register. Run AI-drafted emails through paraphrasing tools targeting Grade 8 for the most natural-sounding professional voice.
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