NapkinBook: the canvas between data and decisions

Anyone can say “likely.” You say 27%. NapkinBook is a digital and computational whiteboard for people who make data driven decisions. Start from the evidance, and update with your beliefs over time. The board does recomputes as you work. Wire in real evidence, then share it so sharper people can try to break it. Free to try. Sign in to save and sync your work. +BASE RATE18%EVIDENCE+9COMBINE→PYOURS27%−CROWD34%GAP−7drag the evidence,the rest recomputes Built by a superforecaster who’s worked with Microsoft AI. 0.19 Brier score vs a 0.28 field average 90% win rate A canvas that computes Circles hold values, squares do the math, wires carry the numbers between them. Nudge any input, and everything downstream, including your final number, recomputes the moment you let go. Live collaboration, end-to-end encrypted Send one link and someone sharper picks up your board with every number still live: same canvas, live cursors, live ink, no accounts to create. The link doubles as the key, so boards stay end-to-end encrypted and the server never sees your work. Present it, phone in hand Turn any board into an authored walkthrough. The camera flies step to step while your phone becomes the remote, carrying the current step, your speaker notes, and what-if sliders the whole room watches you move on the big screen. Uncertainty is a first-class value Base rates counted from real series, p10 / p50 / p90 fans, Monte Carlo bands. The board treats “how sure” as part of the answer, not a footnote. The whole thesis on one board. The base rate, the drivers, your live number, the crowd’s, and the data behind it all sit on one canvas, so you see the whole argument at a glance, not scattered across tabs. Pick a piece and its inspector appears. Let go and the board is clean again. Circles hold values, squares compute, wires carry your number and the crowd’s into a live gap, with the data it rests on right beside it. Made to be argued over, not screenshotted. A thesis is worth more after someone’s tried to break it. Send the link, and whoever’s sharper than you can pull up the same board with every number still live, instead of a stale screenshot in a group chat. When you’re walking a room through your reasoning, hit Present and your phone becomes the remote, carrying the current step, your notes, and what-if sliders the whole room watches you move. The reasoning stays on the board, so when it resolves, you can see why you were right, or how you fooled yourself. RECESSION BY 202734%41%LIVESTEP 3 / 5 The stage screen, a chrome-free view that follows the show full-screen. REMOTE3 / 5RECESSION BY 202734%UP NEXTUnemployment · 1948–nowYOUR NOTELand on your number, then pullthe spread to show the swing.yield spread−1.2−1.9‹› Paired over the link, nothing touches a server One board instead of five tabs. Each of these tools is great at its one job. NapkinBook is where they meet: the data, the math, and your read in one place, where the crowd’s number and yours sit side by side. CapabilityNapkinBookExcalidrawSheetsTableauInfinite freeform canvas Yes Yes No NoLive math on the canvas Yes No Yes PartialProbability & uncertainty bands Yes No Partial NoQuery your own data in SQL Yes No Partial YesForward-looking, not just history Yes No Partial NoReasoning saved beside the number Yes Partial No NoPresent + phone remote Yes No No Partial Built-in With effort Not really Pricing that fits on a napkin. Free $0 /month Every feature: canvas, math, probability, SQL Live collaboration, end-to-end encrypted Present mode with the phone remote Export any walkthrough as a standalone report No account, no metering, no paywall to hit Put a number on your next call. Start from a blank board and land on a number you can defend in minutes. Yours against the crowd’s, the gap live. Nothing to sign up for.