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18" Footprint Checker

Does the robot fit the 18-inch starting cube once the wheels, screw heads and motors are counted rather than just the frame?

Inputs

in

Outer edge to outer edge. A span of N holes is exactly N × 0.5".

in
in

Tallest point, including anything sticking up.

in

Wheels, motors, screw heads, collars. Per side, so it gets counted twice.

in

Per end. Also counted twice.

Results

Fits the cube?

—

Overall length

—in

Overall width

—in

Overall height

—in

Tightest dimension

—

Margin there

—in

Overall width in hole spacings

—

Tightest dimension, against the starting cube—

Everything has to fit inside this at the start of a match, including anything sticking out past the frame.

Stretch the frame

Stretch the framefrom abovefrom the side
15 in

Your robot from above, to scale, inside the starting box. The inner outline is the frame; the outer one adds everything you said sticks out past the sides and ends. Slide the frame longer and watch the outer outline reach the box, with its overhang counted at both ends. On the right is the robot from the side, against the same limit.

When you would use this

  1. We are not sure our robot will pass inspection.

    Measure the frame, then add whatever sticks out past it on each side: bolt heads, standoffs, an intake sitting proud. The tightest dimension is the one inspection will find.

  2. Our intake sticks out and we want to know if it still fits.

    Put the overhang in the sides or ends box rather than guessing. It counts double, because it sticks out on both sides of the measurement.

  3. We want to know how much room we have left for a bumper or a guard.

    The margin figure is exactly that: how many inches you can still add before the tightest dimension reaches the limit.

How this is calculated

The arithmetic is deliberately dull. The value is in what gets counted.

overall length = frame length + (2 × sticking out past each end) overall width = frame width + (2 × sticking out past each side) fits when every dimension ≤ 18"

Note the doubling. A team measures a wheel sticking out an inch and a half on one side, subtracts that from eighteen, and concludes there is plenty of room, forgetting the identical wheel on the other side. Three inches of a fifteen-inch frame's allowance disappears that way.

What people forget to measure

  • Wheels are wider than the frame. Usually the single biggest contributor, and the easiest to leave out because it feels like part of the drive rather than part of the size.
  • Screw heads and nylock nuts. A quarter inch each side, everywhere, and they are on the outside precisely where it costs you.
  • Motors and shaft collars. Motors hung outboard, and collars on shaft ends, both stick out past the structure.
  • Anything that sags. A mechanism held up by a rubber band at rest may not still be inside the cube once it settles.

The diagonal does not matter

A common worry: "my robot is 17 by 17, but the diagonal is 24 inches. Is that legal?" Yes. The robot has to fit inside a cube in the orientation it starts in, and a 17 × 17 rectangle sits inside an 18 × 18 square comfortably. The sizing tool goes around the robot; it is not rotated about it.

Leave yourself room

Designing to exactly eighteen inches means any build tolerance, any slightly bent piece of structure, and any washer you added later puts you over. The robot that measures a comfortable seventeen and a half passes inspection at every event without a conversation.

Sources & assumptions

The 18" starting envelope is from the Override2026-27 game manual. The 0.5" hole spacing is a verified VEX standard, so a span of N holes is exactly N × 0.5".

C-channel outer dimensions are deliberately not built in. They depend on material and thickness, VEX does not publish them in a form I could verify, and a guessed figure here would hand teams a false pass at inspection. Measure your frame and enter what you measured.

Every source the site uses, and when it was checked

Save this run, and compare

Keeps what is on screen so you can change something and see both sides of the change. Saved in this browser only, never uploaded.

Make a notebook page

Turns this calculation into a dated engineering notebook page: the setup, data, results, figures, working and sources, numbered and cited. You add the goal, the decision and the reflection in your own words, plus photos and sketches. Print it, paste it into Google Docs, or download a Word file or slides.

My notebook

Notebook page

More
Open My notebook

    This page

    Our own layouts

    A layout remembers how a page is set up: its type, its system, which parts print and which of your tables it uses. It never remembers a word, a number or a photo.

    Your team kept on this device
    Add someone to the team list
    Your words never written for you

    These are the parts a judge or teacher reads to see your thinking, so the page leaves them to you. Leave a box empty to get lined space for writing by hand. Start lines with "- " for a list. The notes under each box only count and point things out; they never change what you wrote.

    Rough notes

    Rough notes

    Rough notes

    Rough notes

    Rough notes

    Rough notes

    Rough notes

    Rough notes

    Rough notes

    The word counts can be measured against a target your team sets on My notebook. The reading level is Flesch-Kincaid grade level = 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59. Syllables are counted by vowel groups, so the grade is an estimate of the school year the writing reads at. It says nothing about whether the writing is any good.

    One part at a time, with a clock. At the end of practice, while you remember it.
    How you tested your details

    Fill in what applies. These print as a small table under the method.

    Before and after

    Compare this calculation with a run you saved earlier on this tool (under “Saved runs”). The page shows what changed and by how much.

    A line through the data from your recorded table

    Pick two measured columns from the same table. The page plots them and draws the least-squares line, only across the range you measured.

    Robot log a CSV from the robot's SD card

    Load a CSV your robot saved. Pick the time column and up to three columns to plot, and type their units. Only those columns go on the page; the file stays on this device.

    Two versions' trials your data, compared

    Pick a column of recorded trials for each version, from this page or another saved page. The page shows both averages and a 95% range for the difference. The numbers are copied in when you pick them, so later changes to the other page don't change this one.

    Options compared your scores

    Score each option 1 to 5 on each criterion, and weight each criterion 1 to 5 by how much it matters. The page only multiplies and adds.

    Photos and sketches stay on this device

    Up to 4. Paste a screenshot with Ctrl+V, drop pictures here, or pick them. Photos are shrunk before they’re kept, and an unsaved page keeps them in its draft. Use Mark up to draw arrows, labels, dimensions and numbered callouts on a photo. Mark one photo Before and one After to print them side by side.

      Test plan written before testing

      Write this before you test: the question, what you expect with a number, and what result would make you drop the idea.

        Build steps our build

        One row per step, in order, so someone could rebuild from this page.

          Parts used our parts list

          Lengths in holes are also shown in inches between the end holes. Weights are only added up where you type them.

            Plan the cuts: packs every piece of one part (sizes in holes, or inches on the hole grid) onto whole sticks of the stock length you type.

            Ways it could fail our scores

            List the ways this could fail. Score how likely (1 to 5) and how bad (1 to 5); the page multiplies them and puts the biggest risks first.

              Designed against built our measurements

              What the CAD or the plan said, and what you measured on the robot. The tolerance is yours.

                Changes from the last version our changes

                What changed since the last version, why, and which result it was meant to move.

                  That page’s settings, results and first photo are copied in and set beside this page’s. The result each change should move is looked up on both pages.

                  Tasks our plan

                  What needs doing, who, and by when. Open tasks carry to the next meeting page until someone ticks them done.

                    The pages behind this idea our evidence

                    The pages in this notebook that show the idea being tried, measured or changed. A judge reading the claim can turn straight to them.

                      Time spent our hours

                      Who worked on this and for how long.

                        Session log what we did, as we did it

                        Notes taken during a session. The time comes from the clock when the note was taken; every word is yours.

                          Size limit does it fit?

                          Type the starting size limit from the current game manual, and the robot's size as designed or measured, in inches. The site doesn't store the limit, because it changes with the game.

                          What broke from your breakage log

                          The breakage log is on My notebook. Copy it onto this page as a table, as it stands now; later entries don't change this page.

                          CAD model which version this page is about

                          Paste a link to the model (Onshape, Fusion or anything else) and the name you use for this version. For Onshape, the page reads from the link whether it points at a saved version or a workspace that keeps changing. Nothing is fetched.

                          Your code
                          Comments notes for the team, not the page

                          A teammate or coach can leave a note here. Comments stay beside the page, travel with it in exports and links, and don't print unless you tick them under Include.

                            Sources you used besides this tool

                            Videos, other teams, manuals, people. The tool’s own sources are cited for you.

                              Sign-off
                              Include

                              Press a ? to see what an option is for, or read them all on How the notebook tools work.

                              What “The calculator’s figures” is for

                              The calculator’s own diagrams and charts, numbered as figures and drawn from your numbers. Judges look for pictures that explain a design.

                              What “How it was calculated” is for

                              The formulas and steps the calculator used, so a reader can check the arithmetic for themselves.

                              What “The calculator’s warnings” is for

                              Things the calculator flagged, such as a motor near stall. They’re quoted and credited to the calculator, so they never read as your conclusion.

                              What “The calculator’s notes” is for

                              The calculator’s plain-language notes on the result. Off at first, because they read like conclusions, and the conclusions on a page should be yours.

                              What “Lined space” is for

                              Ruled lines under any part you haven’t written yet, so a printed page can be finished by hand.

                              What “Writing space as” is for

                              The blank space for handwriting as ruled lines, a dot grid or quarter-inch squares. Dots and squares suit sketches and hand-drawn graphs.

                              What “A summary under recorded data” is for

                              The number of readings, the average, the spread, the lowest and the highest under each table you recorded, worked out from your numbers. It shows every run counted, not just the best one.

                              What “Words used” is for

                              A small box with the site’s one-line definitions of glossary terms the calculator used, for readers who don’t know them. It never looks at your own writing.

                              What “Robot at the time” is for

                              The Robot Profile as it was when the page was first saved, so weeks later you can tell which version of the robot a test was run on.

                              What “Long tables in full” is for

                              Long calculated tables printed complete on an extra page, instead of every few rows on the page itself.

                              What “Fit on one sheet” is for

                              Smaller type and shorter tables, aiming for one printed sheet. Use it when every entry in your notebook should be a single page.

                              What “Wider left margin” is for

                              A wider left edge, so the page can be hole-punched or bound without losing any words.

                              What “Larger type, for reading aloud” is for

                              Bigger print with more room between lines, for the team member who reads the page to a judge. It overrides Fit on one sheet.

                              What “Our rubric scores” is for

                              Your own scores against the rubric, on a sheet of their own, for checking a page before a judge does.

                              What “When this page was first saved” is for

                              The day the page was first saved, printed beside its date. It shows the notebook was kept while the work happened.

                              What “Teammates’ comments” is for

                              Prints the comments teammates left on this page at the end, marked as not part of the page. Off at first, because comments are notes for the team, not for judges.

                              What “Show every table and block” is for

                              Shows every table and block in the editor, not only the ones this type of page usually uses. It changes the editor, not the printed page.

                              Rubric check

                                This checks what is on the page, not how good it is. Clear, specific writing in your own words is what earns the top marks.

                                Preview, letter size

                                Write it now

                                Where this goes next

                                Explore further on the full map

                                Where the answers on this page can be used, and which tools could have given you the numbers it asks for.

                                Comes after

                                DR4B Geometry CalculatorTwo-Bar LiftSix-Bar Lift

                                You are here

                                18" Footprint Checker

                                Where your answer goes

                                Center of Gravity Locatorfind where the weight sits inside that frameuses your footprint againWhole Robot Design Checkcheck size, power, speed and tipping together in one gobrings your footprint with itTrack Width & Turning Geometrysee how that frame shape changes the way the robot turnsDR4B Geometry Calculatorcheck a double reverse four-bar still folds inside the starting size

                                a number carries across the next question it raises

                                Keyboard shortcuts

                                Anywhere

                                Ctrl K or /
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                                T
                                Switch color theme
                                B
                                Bigger text, for a projector
                                F
                                Readable font, on or off
                                ?
                                This list

                                On a tool

                                S
                                Star or unstar it
                                C
                                Copy the results
                                L
                                Copy a link to these exact numbers
                                P
                                Print or save as PDF

                                Letter keys do nothing while you're typing in a box.