Seattle Ultrasonics · AngleGenie

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    Ten minutes to a sharper knife

    Wake AngleGenie, zero it on your stone, pick your knife, then sharpen with the angle in your ear. The app walks you through every step.

    • A whetstone, soaked if it needs it, on a towel so it stays put.
    • A knife. The app supports culinary knives, outdoor knives, folding knives, and many others.
    • AngleGenie, awake: one click of its button.

    Recent sessions

      So far

        My knives

          Pick one while you sharpen and it is kept here.

          Train

          Library

          The Library remembers your knives over time: each one’s wedge angle, so the guide shows the true edge angle, and the last sharpening angle you used, ready for next time. Kept on this device, and in your account once you sign in, so they follow you to any device.

          Kept on this device.

          My knives

          No knives yet. Add one below, or pick one while you sharpen and it is kept here.

            History

            No sessions yet. Every finished session lands here.

              This content is placeholder, pending real human-crafted replacement.

              Learn

              Sharpening technique

              Ten short lessons, in the order the questions come: the burr, the flip, the stones, the paper, and what a sharp edge looks like up close. Two or three minutes each. The same lessons answer the guide’s “why” during a session.

                AngleGenie User Manual

                The user manual as short articles: what is in the box, safety, mounting and connecting, the zero and the angle, reading the guide, the light, the battery, and what to do when something looks wrong.

                  Settings

                  Saved on this device.

                  Appearance

                  Theme—
                  UnitsStroke distances and knife sizes: centimetres and millimetres, or inches and feet.

                  Guide

                  Step-by-step guidanceTips and pointers on screen during your session.
                  SoundOff is mute: the screen and AngleGenie’s light still show the angle.
                  SoundscapeHear each one, and pick.
                  Sound only on the stoneQuieter while the blade is off the stone.
                  Tolerance zoneHow far off angle still counts as on angle: the green band.
                  Distance markersA soft chime and a dot each time a side passes this much stroke distance.
                  Angle precisionIncrement for the angle picker and the live readout.
                  Keep screen awakeHold the display on while AngleGenie is connected.

                  Account

                  Your knives and history are kept on this device. Sign in to back them up to your account, so they follow you to any device or browser. Sharpening itself never needs an account.

                  Privacy

                  Your browser is sending a Global Privacy Control signal, so we’ve turned this off. You can turn it back on if you want to.

                  Send session dataSends your completed sessions (motion data, angles and device details) to the cloud so we can improve the sharpening guidance. Your on-screen guidance is worked out on your own device and works the same either way. Read the agreement

                  Nothing is sent until you accept the agreement, which comes up the first time you connect AngleGenie.

                  Help

                  About

                  License agreement · ·

                  © 2026 Seattle Ultrasonics ·

                  Start over: delete everything AngleGenie keeps on this device and see the app as on a first launch. Signed in, you are signed out first; what your account holds stays there.

                  Your AngleGenie

                  Language

                  LanguageEnglish or French, the device’s own unless you choose. The app restarts in the language you pick.

                  Diagnostics

                  Export the session that just finished, or load a recorded session (JSON) to replay its IMU stream through the full experience.

                  cloud: —

                  No file loaded.

                  accel: —

                  gyro: —

                  roll: —

                  stream: —

                  device: —

                  contact: —

                  Ground truth: hold the ANGLEGENIE BUTTON (or SPACE) while the blade is truly on the stone.

                  Console

                  This content is placeholder, pending real human-crafted replacement.

                  1:55 CC

                  Meet AngleGenie

                  A two-minute tour, from the stone to your first stroke.

                  The video is on its way. Until then, those five steps are the tour, and each screen walks you through its part when you get there.

                  You can watch it again any time from Settings.

                  Pick a theme

                  The guide’s own settings, like the angle precision, stay as you set them whichever theme is on.

                  Tap a theme to hear it

                  Classic · 8-bit

                  Sharpen

                  Today’s sharpening

                  Raise a burr on both sides, refine the edge, then paper test.

                  Stones

                  Coarse to fine. Tap the ones you’ll use: the guide says when to move on, and the record keeps each.

                  Coarse
                  Medium
                  Fine
                  Polish
                  After the stones

                  1000 → 6000 → strop

                  How AngleGenie helps

                  Pick one, then Next. The sound guides you either way; this only decides whether the steps are said.

                  1. Connect
                  3. Zero
                  5. Blade
                  7. Angle
                  1

                  Wake your AngleGenie

                  1. 1Click its button once. The light blinks in pairs while it looks for your device.
                  2. 2Press Connect and pick it from the list. The stone comes next.

                  Not in the list? AngleGenie sleeps after a minute on its own. Click its button again.

                  1. Connect
                  3. Zero
                  5. Angle

                  Wake your C-200

                  1. 1Slide the battery pack out of the handle and push it back in. The knife looks for your device for thirty seconds.
                  2. 2Press Connect and pick C-200 from the list. Its sensor is in the handle, so there is nothing to attach.

                  Not in the list? Take the battery pack out and put it back, then press Connect again.

                  Connected

                  Before your first session

                  Please read and accept the AngleGenie agreement. Here’s the short version:

                  Safe: keep your eyes on your hands.AngleGenie and this app are no substitute for safe knife handling.
                  It runs on your device.The guide works out every angle right here, with or without an internet connection. Signing in is optional: it only keeps your knives and history with you.
                  Supervision required.Sharpening is sharp work. Keep AngleGenie, the knives and the stones out of children’s hands.
                  Send session dataMotion data and results from each session help us improve the guidance. Turn it off any time in Settings.

                  Your browser sends a Global Privacy Control signal, so this starts off.

                  Connected

                  Update AngleGenie

                  Checking for firmware updates…

                  Firmware

                  —

                  Required

                  Preparing…

                  Keep this page open and AngleGenie nearby until the update finishes.

                  1. Connect
                  3. Zero
                  5. Blade
                  7. Angle
                  12
                  0°
                  Flat on the stone reads 0°

                  Zero it on the stone

                  1. 1Lay AngleGenie flat across the stone, parallel to its short edge, button up.
                  2. 2Click its button, or tap Zero now, then hands off: it needs two seconds of stillness.

                  Waiting for a click

                  1. Connect
                  3. Zero
                  5. Angle
                  12
                  Handle flat on the stone reads 0°

                  Zero the knife on the stone

                  1. 1Lay the knife on its side, the handle flat on the stone and the blade off the end, in the air. Never lay the blade on the stone: it scratches.
                  2. 2Press its handle button, or tap Zero now, then hands off: it needs two seconds of stillness.

                  Waiting for a click

                  1. Connect
                  3. Zero
                  5. Blade
                  7. Angle
                  12

                  Zero saved

                  Put it on the blade

                  1. 1On the flat of the blade, near the spine and above the heel. The magnets hold it.
                  2. 2Button up, arrow toward the tip. The words may read upside down, but that’s correct.

                  Click its button, or Next below, and set the angle.

                  Waiting for a click

                  Freehand Two acts: unguided first, then with the guide, each as long as you like. 0 s
                  Turn your volume upThe angle guide is mostly sound: it tells you where the edge is without looking at the screen.
                  Lift the blade toward 15° Side A
                  Target 15° ± 3°

                  Freehand vs. Guided

                  You'll be asked to sharpen at 15° with no feedback, for as long as you like.

                  Then switch the guide on and keep going. Show your results when you're done.

                  Or click AngleGenie’s button once your hands are on the knife.
                  Sharpen by feel. Switch the guide on whenever you are ready. 0 s
                  Side A · 0 cm 0 cm · Side B
                  Utility level
                  X · along
                  Y · across
                  Set AngleGenie on the surface, button up. X runs along it, Y across.
                  Your AngleGenie

                  No AngleGenie has connected to this app yet.

                  Firmware update

                  No firmware updates are published yet.

                  This unit

                  Serial number—
                  Firmware—
                  Hardware—
                  Battery—
                  Certificate—

                  Soundscape

                  Tap a sound to use it; play hears it without a session.

                  1. Connect
                  3. Zero
                  5. Blade
                  7. Angle
                  Change knife

                  What are you sharpening?

                  My knives

                  Kept on this device.

                    Or a kind of knife

                    A generic knife: the app assumes its blade and a usual angle, and says which.

                    1. Connect
                    3. Zero
                    5. Blade
                    7. Angle
                    Angle

                    Choose your angle

                    Your C-200 is the knife: its sensor is in the handle, so there is nothing to choose and nothing to attach. Set the edge angle it should steer you to.

                    Bevel

                    Both faces are ground to the edge; the angle below is per side.

                    Edge angle, per side

                    15° a side
                    Last used
                    SharperMore durable
                    Edge cross-section, close up30° included angle

                    Rest the edge on the stone at the angle you want and hold it there. Once it holds still for three seconds, the angle is read.

                    — 3

                    Waiting for AngleGenie…

                    Find your knife

                    AngleGenie sits on the blade’s face, and on a wedge-shaped blade the face runs a little steeper than the edge. Knowing the blade lets the guide show your true edge angle.

                    Sign in to search the knife database. Thousands of knives by brand and model, each with its real blade numbers, for signed-in users. Sign in to search them, or add your knife by hand under Add manually.

                    Type to search the knife database.

                      Saved with the typical wedge until it is measured. For the exact figure, measure it with AngleGenie:

                      Step 1 of 3AngleGenie not connected

                      Cover the stone

                      Lay a sheet of paper or a paper towel over the stone, so the blade never touches it.

                      Full wedge— Offset—
                      Wedge offset — Select or describe a knife.
                      Session results

                      —

                      —

                      15°edge, a sidebevel

                      Freehand vs. guided

                      —

                      FreehandGuided
                      Strokes——
                      Average angle held——
                      Accuracy mean off target——
                      Stability stroke-to-stroke——
                      Bias steep + / shallow −——
                      On angle——

                      Stroke motion by angle

                      — on angle

                      stroke motion on angle

                      Sharpening time—active sharpening
                      Total stroke—both sides
                      Side A——
                      Side B——

                      Stones—

                      Strokes, side by sidegreen on angle, amber near, grey off

                      Side ASide B

                      By stone

                      Scratch patternstroke direction against the edge

                      Angle Flashcards

                      Hold the knife in the air, edge down, as if it were on the stone. When a card appears you have three seconds to match its angle. Then it tells you how close you were, and deals the next one.

                      Card 1 of 7 HI 0 0 pts
                      Target —° / side You held —°

                      Press Start when you are ready.

                      Off by— Wobble— —points
                      Flashcard results

                      — pts

                      of 700

                      Average miss—degrees off target
                      Average wobble—steadiness during the hold

                      Card by card

                        Lesson

                        Sign in

                        Your knives and history are kept on this device. Sign in to back them up, so they follow you to any device or browser. Sharpening never requires an account.

                        Choose your device

                        Looking for an AngleGenie or a C-200 nearby…

                          Sign in

                          Your knives and history then follow you to any device or browser. Sharpening itself never requires an account.

                          Stones

                          Move on when both sides have a burr on the stone you are on.

                          Tap the stones you’ll use from here.

                          Guide
                          Step-by-step guidanceTips and pointers on screen during your session.
                          SoundOff is mute: the screen and AngleGenie’s light still show the angle.
                          ThemeThe look of this screen, and the sound it brings.
                          Soundscape—
                          Sound only on the stoneQuieter while the blade is off the stone.
                          Tolerance zoneHow far off angle still counts as on angle.
                          Angle precisionIncrement for the live readout and the angle picker.
                          Distance markersA soft chime and a dot each time a side passes this much.
                          Keep screen awakeHold the display on while AngleGenie is connected.

                          Everything else is in Settings, once you finish.

                          Reading your results

                          The big number

                          “46% on angle” is the share of your stroke motion that landed inside the target band. It is measured by distance travelled, not by time, so resting the blade at a perfect angle without moving it cannot inflate the number, and only motion detected on the stone counts at all.

                          It is a description, not a grade. A lower number on a tight band can be better sharpening than a high number on a loose one, which is why the band it was measured against is printed right underneath it.

                          Edge angle and the face AngleGenie sits on

                          AngleGenie sits on the blade’s face, and on a wedge-shaped blade the face runs a little steeper than the edge. The zero is taken with AngleGenie flat on the bare stone, so it reads the face’s true tilt, and the guide takes the knife’s wedge offset off to show your edge angle. The typical kitchen knife is about 1.5°; naming the knife uses its real spine thickness and height, or the offset you measured with AngleGenie.

                          The curve

                          Every stroke is filed by how far off your target angle it was, and the height of the curve is how much blade travel landed there. A tall narrow peak means a consistent angle; a wide or lumpy curve means the angle wandered.

                          The green band is your tolerance zone and the orange dashed line is your exact target. Anything left of the band was shallow (spine too low, a wider edge); anything right was steep (spine too high, a narrower, more fragile edge).

                          The small V icon above the curve splits it into your two bevel sides, drawn on one scale. Peaks in different places means one side ran steeper than the other, which is what leaves an off-centre edge.

                          Detail

                          Per side, the mean is the distance-weighted average of your angle error and the spread one standard deviation of it; strokes are the ones AngleGenie closed at each turnaround and readings the on-stone samples behind the curve. The scratch pattern is where your strokes ran against the edge: 90° is straight across, which leaves strong teeth; 0° or 180° is along the edge, which leaves grooves the edge chips along. The orange ray is the aggregate angle.

                          Freehand vs. guided

                          Accuracy is how far each stroke sat from the target, averaged. Stability is how much that varied from stroke to stroke. Bias says which way you drift when nobody is watching: positive is steep, negative is shallow. The percentages are how much better (or worse) the guided strokes were on each.

                          What to change next time

                          Mostly shallow? Raise the spine slightly. Mostly steep? Lower it. A wide curve rather than an offset one is a steadiness problem, not an aim problem: slow the stroke down and let the sound guide you. And if the score looks unrealistically low, check that the tolerance in Settings matches the edge you actually want.

                          Which knife was it?

                          The session is filed under the knife you name, in History and in My Knives.

                            Type to search the knife database, or just give it a name.

                              License agreement