about sum28
sum28 is a california real-estate technology company operated by SUM 28 LLC. it builds trust instruments — products that make claims about real estate checkable: p2d (listing copy verified against photos), ohm (open houses measured for the seller), and oak (home equity accounted annually). it sells the instrument and the proof — never advertising, leads, or data about people.
what does sum28 make?
three instruments. each name is lowercase, three letters or fewer, and each subtitle ends in a past participle — because each hands you a completed fact you can give to a client, a seller, an heir:
- p2d — photo to description, verified. listing copy written from your photographs, every sentence traced to evidence. live.
- ohm — open house, measured. a thirty-second sign-in that becomes a seller's report. july 2026.
- oak — equity, accounted. an annual statement for the home, stated as a range. january 2027.
what does the name mean?
Σ 1 + 2 + 4 + 7 + 14 = 28.
28 is a perfect number: it equals the sum of its own divisors. Σ is the sum. a sum that checks out — the whole company is in the name.
the thesis
our read of the decade is short: cognition is going to zero; liability is not. anything that merely writes, summarizes, or predicts will be given away. what stays scarce is the sentence a professional will sign — checked against evidence, priced with a range instead of a guess, safe to hand across a table. so we don't sell generation. we sell the instrument, the check, and the seal — for the one industry where a single unverified sentence can cost six figures.
the constitution — five commitments
- we will never sell advertising inside an instrument.
- we will never sell a lead, a list, or a person.
- we will never take per-lead fees from lenders, escrow, or title.
- we will never state a point estimate where the honest answer is a range.
- we will never risk the trust that prices our name.
restraint is not a style here. it is an epistemology: we do not say more than the evidence allows.
how does sum28 verify its work?
every artifact we produce closes with one bronze mark — the seal. scan it, and the evidence opens: the sources we checked, the checks that passed, the error budget we publish. behind it sit three disciplines: voice, market statistics, and facts kept physically separate (prose may never exceed its evidence); an independent calibrated verifier measured against human adjudication at false alarms under 10% and recall 1.0; and a fair-housing review of every sentence, in english and in chinese, before anything ships.
company facts
- legal name: SUM 28 LLC, a california company
- products: p2d (live) · ohm (july 2026) · oak (january 2027)
- general contact: hello@sum28.com · privacy requests: info@sum28.com
- we answer directly — sum28 is a small team, and support is not outsourced