Free calculator · Venture & Startup Finance
Antidilution, Who Absorbs a Down Round
Calculates how a down round resets the preferred’s conversion under full-ratchet versus broad-based weighted-average antidilution, and what each protection does to founder ownership. Inputs are the Series A share count and original price, the down-round price, founder shares, and the new shares issued.
By Devon Coombs, CPA, MBA · Teaching Professor of Finance, Santa Clara University · Reviewed August 2026
From the author: Devon Coombs, CPA, MBA teaches finance at Santa Clara University and works with corporate teams on practical AI.
AI training for finance teams · Consulting · The 10 Laws of Finance
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Antidilution, Who Absorbs a Down Round
No protection
72.7%
founder ownership
Broad WA
72.1%
market standard
Full ratchet
61.5%
harshest for founders
Full-ratchet Series A shares
4.00M
$10.0M ÷ down price
Broad-WA conversion price
$4.77
falls only modestly
Full ratchet resets the earlier investor's conversion price to the new low price regardless of round size, doubling their shares here. Broad-based weighted average scales the adjustment to the size of the down round, and is the market standard.
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Built by Devon Coombs, CPA, MBA, Teaching Professor of Finance at Santa Clara University.