Construction calculator for your phone
The jobsite calculator that shows its working.
Feet, inches and fractions, the way they read off a tape. Ask it a question in plain English. Get the answer, a drawing to scale, and every step of how it got there.
Runs on any phone, tablet or computer. Nothing to install. Works with no signal.
Demo
See it in one minute
Recorded on a phone, exactly as you'd use it
- Feet, inches and fractions, or just ask in plain English
- Solvers that show every step, and the reason for it
- Material lists and bids at your own prices
Features
Built for the tape measure, not the classroom
Every extra key press is another chance to fat-finger a number with gloves on. Jobsite Sidekick was shaped by a working carpenter and a site superintendent who tested it against the calculator already in their pocket.
A keypad that speaks feet, inches and fractions
Dedicated FEET and INCH keys and a row of one-tap fractions, most-used first. 12' 6-1/2" takes five presses. The same entry took our tester eight on his handheld construction calculator.
| 12' 6-1/2" + 8' 9-3/4" | 21' 4-1/4" |
| 20' × 12' × 4" | 2.963 cu yd |
| 12.35 then AS FT | 12' 4-3/16" |
| 1 m + 12" | 4' 3-3/8" |
| 240 sq ft + 10% | 264 sq ft |
Ask it like you'd say it
No formulas to remember. Type the question, or use your phone's dictation, and Jobsite Sidekick picks out what you're asking for and the measurements you gave it.
| How many 16 inch studs in 20 feet? | 15 |
| Diagonal of 12 ft by 16 ft | 20' |
| Half of 21' 8" | 10' 10" |
| Add 10% to 320 sq ft | 352 sq ft |
| Convert 8 feet to mm | 2438.4 mm |
It always shows what it worked the question out as, so it never quietly reinterprets what you asked.
Solvers that show every step, and why
Pick a job, fill in whatever you happen to know, and the rest fills itself in. Give it pitch and span and it gives you the rise, the rafter length and every cut angle. Give it rise and run and it gives you the pitch.
- Each step shows the formula, the numbers that went in, and a plain sentence on why that rule applies
- Works forwards or backwards from whatever you've measured
- Tells you plainly what is still missing instead of guessing
- Flags the things worth a second look, like a riser over 7-3/4"
See it drawn to scale
A stringer drawn in true proportion with its dimensions on it is easier to check than a column of figures. A 16-riser stair draws sixteen steps. A 12/12 roof draws at 45°.
- Scale drawings for common rafters, jack rafters, stairs, right triangles, slope and squaring
- Side-cut answers include the number to pair with 12 on a framing square
From a measurement to a price
More than the arithmetic
Material take-offs
Enter one wall, floor, roof or pour and get everything it takes to build it, in the units it's sold in. Every rule of thumb, from waste to nails per stud, is yours to edit.
Days, cost and bid
Turn an amount of work into working days, your cost, and what to bid. Cost and bid stay separate so your margin is never hidden. It uses your supplier's prices, not ours.
Saved jobs you can name
Keep the running tape and any solver result under a name you'll recognise on site, then share it as plain text that survives a text message or a supplier's order form.
Works with no signal
Basements and new builds don't have bars. Open Jobsite Sidekick once and it keeps working offline. Add it to your home screen and it opens like any other app.
Imperial and metric together
Mix feet, inches, metres and millimetres in one sum. Every length answer also shows in decimal feet, inches and millimetres. Round to an 8th, 16th or 32nd.
AI tutor
A tutor that explains the working in your own words and answers follow-up questions, built on the calculator's checked arithmetic. Included for subscribers when it arrives.
28 solvers
The jobs it already knows
Framing and concrete first, because that's where the hard maths lives. More trades are on the way.
Framing
- Common Rafter
- Hip / Valley Rafter
- Jack Rafters
- Stair Layout
- Stud / Joist Layout
- Squaring / Diagonal
- Board Feet
- Sheet Goods
- Arch / Circle Segment
- Crown Compound Angles
Concrete
- Slab on Grade
- Strip Footing
- Round Column / Pier
- Concrete Wall
- Rebar Grid (#3 to #11)
- Block Wall
Geometry
- Circle / Round
- Slope & Grade
- Right Triangle
- Regular Polygon
Materials
- Exterior Wall
- Interior Wall + Drywall
- Floor / Deck Frame
- Roof Covering
- Concrete Floor
- Concrete Wall
- Concrete Steps
Days & Cost
- Working days
- Labour cost
- Overhead
- Profit
- What to bid
Example
Watch it work a real job
A 30' × 24' garage slab, start to finish
- Forms squared, with the diagonal drawn to scale
- Yards to order, with waste added and every step shown
- The full order list priced, then turned into a bid
Compare
How it stacks up
The established construction calculators are good tools. Here is where Jobsite Sidekick is different.
| Jobsite Sidekick | Construction Master Pro app | Construction Master Pro handheld (4065) | BuildCalc | Phone calculator | |
|---|---|---|---|---|---|
| Price | $3.99/mo or $29/yr | $4.99/mo or $39.99/yr | $74.95 once | $24.99 once | Free |
| Feet, inches and fractions | ✓ | ✓ | ✓ | ✓ | No |
| Stair and rafter solvers | ✓ | ✓ | ✓ | ✓ | No |
| Material take-offs | ✓ | ✓ | ✓ | ✓ | No |
| Ask a question in plain English | ✓ Works offline | AI help (Ask CMPro) | Keypad only | — | No |
| Step-by-step working with the reason for each step | ✓ Every solver | AI guidance (Ask CMPro) | — | — | No |
| Answer drawn to scale | ✓ Six solvers | — | — | Stair drawings | No |
| Saved work | ✓ Named jobs, shareable | ✓ Tape, save and share | Tape and memory keys | ✓ Saved results | No |
| Works with no signal | ✓ | — | ✓ | — | ✓ |
| How you get it | Opens in your browser | App download | Separate device to carry | App download | Already on your phone |
A dash means the feature is not mentioned in that product's own listing; it may still exist. Prices in US dollars, taken from each maker's website or App Store listing on 5 October 2026, and may have changed. Construction Master is a trademark of Calculated Industries, Inc. BuildCalc is a product of its respective owner. Jobsite Sidekick is not affiliated with or endorsed by either.
Pricing
One plan. Everything in it.
Try it on a real job for 7 days. Cancel any time.
- Feet-inch-fraction calculator
- Plain-English ask box
- All 28 solvers with full working
- Scale drawings
- Material take-offs
- Days, cost and bid
- Saved, shareable jobs
- Works offline
- Every new solver and trade we add
- The AI tutor when it launches
Getting started
On your phone in two minutes
Start your free trial
Pick monthly or yearly and sign up here on the website. Payment is handled securely by Paddle, our reseller.
Open Jobsite Sidekick on your phone
It runs in the browser you already have, on iPhone or Android. There is no app store and nothing to download.
Add it to your home screen
One tap puts the Jobsite Sidekick icon next to your other apps, and it keeps working when the signal doesn't.
FAQ
Fair questions
Is this an app I download from the App Store or Google Play?
Not yet. Jobsite Sidekick is a web app: it opens in your phone's browser and you can add it to your home screen, where it looks and behaves like an installed app. That means it works on iPhone, Android, tablets and computers from day one.
Does it really work with no signal?
Yes. Open it once while you have a connection and it stores itself on your phone. After that the calculator, the ask box and every solver work offline.
How does the free trial work?
You get the whole app for 7 days. If you cancel before the trial ends you are not charged. After that it is $3.99 a month or $29 a year, whichever you chose.
Can I cancel?
Any time, yourself, in a couple of taps. You keep access until the end of the period you have paid for.
Where are my saved jobs kept?
On your device, in your browser. They do not follow you to another phone, and clearing your browsing data removes them. Use Share to send a copy of any job somewhere safe.
Does it tell me what materials cost?
No, on purpose. Prices change and every merchant is different, so Jobsite Sidekick works out the quantities and you type in your own supplier's prices once. It remembers them until you change them.
Can I rely on it for code compliance?
No. Riser limits, bag yields, lap lengths and similar figures are common North American rules of thumb, shown as editable values and advisory warnings. Codes vary by jurisdiction. Anything structural should be confirmed against your local code and the engineer of record.
Is the plain-English ask box an AI chatbot?
No. It is rule-based and runs on your phone, which is why it works offline and gives the same answer to the same question every time. The AI tutor is a separate feature that is still being built.
Measure twice. Calculate once.
Put it up against the calculator in your pocket on your next job.