Voltly
Field calcs you'd wire to — code cited, all offline.
Code-true electrical answers on any job — voltage drop, ampacity, conduit fill, box fill, bending — each citing the NEC article, 100% offline.
Voltly offers an auto-renewing subscription. Payment is charged to your App Store or Google Play account; it renews automatically unless cancelled at least 24 hours before the period ends, and you can manage or cancel anytime in your account settings. Terms and Privacy Policy.
Voltly
productivity
Field calcs you'd wire to — code cited, all offline
Account
Not required
Analytics
Opt-in & anonymous
Your data
Stays on device
Ads & trackers
Zero
What you get
Built for exactly this — and nothing you don't need.
Stop second-guessing your numbers
eight field calculators on one glove-friendly hub: Voltage Drop, Wire Ampacity, Conduit Fill, Box Fill, Conduit Bending, Motor FLC, a converter suite and Ohm's Law. Voltage Drop and Ohm's Law are free; the rest unlock with Pro.
Wire to the number with confidence
every result names the NEC article behind it (Table 310.16 ampacity, 314.16 box fill, Chapter 9 conduit fill), so you can defend the answer to any inspector.
Size conductors right the first time
Voltage Drop runs 1Ø/3Ø in copper or aluminum, flags anything over the 3% recommendation and suggests the upsize; Wire Ampacity uses Table 310.16 with selectable 60/75/90°C termination columns and derate factors.
Bend it once
offset, three-point saddle and 90° stub math hand you the marks before you reach for the bender, so you stop scrapping conduit.
Skip the conversion math
Motor FLC returns full-load amps with 125% conductor and OCPD sizing, plus a converter suite for units, AWG↔mm² and kVA.
Look up code with zero bars
an offline NEC reference of the tables and articles electricians check daily, in plain language with the article number cited; works in basements, panel rooms and steel buildings with no signal and no account.
Never lose a calc
save results into jobs organized by site, panel or circuit in an on-device store; the free tier keeps your last 5, Voltly Pro is unlimited.
Hand off clean paperwork
export any result as a labeled PDF job sheet and turn on iCloud sync (both Pro); tune theme, accent, imperial/metric units and NEC edition (2020 / 2023 / 2026) in settings.
A look inside
See it in your hands.
How it works
Up and running in under two minutes.
- 01
Open the calculator hub and pick a tool — the two free calcs open directly; tapping a locked Pro calc routes to the paywall.
- 02
Enter the job with segmented controls, size pills and steppers — no fiddly keyboard — and the result updates live.
- 03
Read the authoritative readout with its status, the formula used, and the NEC article it derives from.
- 04
Save the result to a job (organized by site/panel/circuit) or look it up later in the offline NEC reference — everything stays on the device, no account needed.
A note from the studio
“Electricians work gloved, in bad light, in dead zones — and still pay for a drawer of dated, single-trick apps to get one number. I wanted a single instrument that's fast, fully offline, and cites the code on every result, so you can wire to the answer and prove it to the inspector. That's all Voltly is: the whole drawer, done right, in one app.”
Questions
The honest answers.
Is Voltly free?
Yes — the Voltage Drop and Ohm's Law calculators, the free-tier NEC reference entries and your last 5 saved calcs are free forever, with no account. Voltly Pro unlocks the other six calculators and unlimited saved jobs.
Is it a subscription or a one-time purchase?
Voltly Pro is a one-time $9.99 Lifetime unlock — pay once, yours forever. If you'd rather subscribe, there's an optional annual plan ($49.99/yr) or monthly ($6.99/mo), both with a 7-day free trial. No subscription is required to own Pro.
Does Voltly work offline?
Completely. Every calculator, table and code reference lives on your phone, so it works in basements, mechanical rooms and dead zones — no signal, no login, no waiting.
Can I trust the numbers?
Voltly uses commonly-published NEC values and shows the formula and the cited article on every result, so the answer is always traceable. It's a field aid — always verify safety-critical results against the currently adopted NEC and your local amendments.
Do you collect my data or show ads?
Never. No ads, no data sale, no account or sign-in. Your jobs and calculations stay in an on-device store; anonymous analytics and crash reports are both opt-in and off by default.
What platforms does Voltly run on?
Voltly is on the App Store for iPhone, built natively for the job site. An Android build runs on the same calculation engine and code reference.
How is it different from Ugly's or Electrical Calc Elite?
Most tools give you live calculators or static code tables — Voltly bundles both in one fast, modern app: working calculators with the NEC article cited on every result, fully offline, for a single $9.99 unlock.
What does Voltly Pro unlock?
All eight calculators (Wire Ampacity, Conduit Fill, Box Fill, Conduit Bending, Motor FLC and the converter suite on top of the free pair), unlimited saved jobs, labeled PDF job-sheet export, iCloud sync and the full offline NEC reference.
Launching soon
Be first to know when Voltly ships.
It'll launch at $9.99. Free tier: voltage drop and ohm's law calculators, free-tier nec entries, and the last 5 saved calcs — no account, fully offline..
One email when it lands on the store. No drip sequence, no spam.
No spam. No tracking. Email only — unsubscribe with one click.
Your saved calculations, jobs and preferences are stored locally on your device (an on-device SQLite database plus app preferences). There is no server copy.
From the journal
Notes on the practice.
- 01
200 Amp Service Wire Size: The 83% Rule That Lets a "Too Small" Wire Feed Your Whole House
What size wire for a 200 amp service? The NEC's 83% rule lets 2/0 copper carry it all — here's the load-diversity physics that makes an undersized wire legal.
2026-07-13
7 min read
- 02
Open Neutral Symptoms: The One Electrical Failure No Breaker Can See
Open neutral symptoms — lights blazing in one room, dim in another, electronics dying — trace to a single failed wire. Here's the physics, and how to test for it.
2026-07-12
7 min read
- 03
Bootleg Ground: The Fake Ground That Fools Every Outlet Tester
A bootleg ground makes a three-light outlet tester read 'correct' on a receptacle that can put 120 volts on an appliance's metal skin. Here's how to find one.
2026-07-12
7 min read
- 04
What a Ground Rod Actually Does: Why Eight Feet of Copper in the Dirt Can't Trip a Breaker
What a ground rod actually does — and why it will never trip a breaker. The Ohm's law math behind NEC 250.53, and the wire that really protects you from shock.
2026-07-11
7 min read
- 05
Backfeeding a Generator: Why a Double-Male Cord Can Kill a Lineman Half a Mile Away
Backfeeding a generator through a dryer outlet can push 7,200 volts onto a line crews believe is dead. The physics — and the one-sentence NEC rule that prevents it.
2026-07-11
7 min read
- 06
Inductive Kickback: Why a Switch Arcs When You Turn Off a Motor or Coil
Inductive kickback explains why a switch arcs when turning off a motor or coil — the back-EMF spike, why DC is worse, and how flyback diodes and snubbers stop the burn.
2026-07-10
6 min read
- 07
Can You Put a 15-Amp Receptacle on a 20-Amp Circuit? The Code Answer and the Physics Behind It
Yes — a 15-amp receptacle on a 20-amp circuit is legal under NEC 210.21(B)(3). Here's the real reason why, and the one case where it quietly becomes dangerous.
2026-07-10
7 min read
- 08
Arc Flash Boundary Explained: Why a Panel Can Burn You From Two Feet Away
Arc flash boundary explained in plain language: why an energized panel can put a second-degree burn on your face without you ever touching a conductor.
2026-07-10
7 min read
- 09
NEC Tap Rules Explained: Why a Conductor Can Legally Have No Breaker at Its Source
NEC tap rules explained: why the 10-foot and 25-foot tap conductors in your panel are legally unprotected at their source — and the trade the Code made to allow it.
2026-07-09
7 min read
- 10
Harmonic Currents and the Overloaded Neutral: Why the Neutral Can Carry More Current Than the Hots
Harmonic currents on the neutral wire can make it run hotter than the phase conductors it serves. Here's why the neutral overloads, and how NEC 310.15(E) tells you to size for it.
2026-07-09
7 min read
- 11
Power Factor Explained: Why a Motor Draws More Current Than Its Wattage Suggests
Power factor explained for electricians: why an inductive load pulls more amps than its watts predict, how reactive power fills the wire, and how capacitors correct it.
2026-07-08
6 min read
- 12
Aluminum Wiring Fire Risk: Why the Metal in Your Walls Loosens Its Own Connections
Aluminum wiring fire risk isn't about the wire melting — it's about connections that quietly loosen themselves over years. Here's the physics, and what to check today.
2026-07-08
7 min read
- 13
Skin Effect Explained: Why a Bigger Wire Doesn't Carry Proportionally More Current
Skin effect explains why AC current crowds toward a conductor's surface, so doubling the copper doesn't double capacity. Here's the physics — and why electricians run parallel conductors instead of one giant wire.
2026-07-07
6 min read
- 14
Paralleling Conductors: Why Two Wires Sharing a Load Must Be Identical Twins
Paralleling conductors under NEC 310.10(H) demands identical length, size, and material. Here's the impedance physics behind why one mismatched wire can quietly overheat.
2026-07-07
6 min read
- 15
Locked Rotor Current: Why a Motor Draws Six Times Its Running Current at Startup
Locked rotor current explains why a motor pulls six times its running amps at startup and why your lights dim when the AC kicks on. Here's the physics.
2026-07-07
6 min read
- 16
Why LED Lights Glow Faintly When the Switch Is Off: The Ghost Current in Your Walls
Why do LED lights glow when switched off? The culprit is a few microamps of leakage current your old incandescent bulb quietly swallowed. Here's the real physics — and the fix.
2026-07-06
7 min read
- 17
Phantom Voltage: Why Your Multimeter Reads 40 Volts on a Wire That's Dead
Phantom voltage on a dead wire fools good electricians every day. Here's the physics of ghost voltage, why your meter lies, and how to prove a conductor is truly de-energized.
2026-07-06
6 min read
- 18
Why the Ground Wire Is Smaller Than the Hot Wire: The Physics Behind NEC Table 250.122
Why is the ground wire smaller than the hot wire? The physics of fault current, I²t heating, and NEC Table 250.122 — plus the one case where you must upsize it.
2026-07-04
6 min read
- 19
Why a 240-Volt Circuit Doesn't Need a Neutral: Split-Phase Power Explained
Does a 240V circuit need a neutral? Usually not — and the reason lives inside a center-tapped transformer. Here's the physics your water heater and dryer cord depend on.
2026-07-04
7 min read
- 20
AWG Wire Gauge Explained: Why Smaller Numbers Mean Bigger Wire
AWG wire gauge explained: why 12 AWG is bigger than 14, where the backward numbers came from, and the doubling rules that let you size wire in your head.
2026-07-04
7 min read
- 21
Motor Circuit Breaker Sizing: Why the Breaker Can Be Twice the Wire's Ampacity
Motor circuit breaker sizing breaks the rule every electrician learns first: the breaker can be 250% of the wire. Inside NEC 430's split-protection logic.
2026-07-03
7 min read
- 22
How an AFCI Breaker Works: Detecting the Arc a Regular Breaker Can't See
How does an AFCI breaker work? Inside the electronics that recognize an arc's electrical signature — and why a standard breaker never sees the fault at all.
2026-07-03
7 min read
- 23
How a Thermal-Magnetic Circuit Breaker Works: The Two Trips Inside Every Breaker
How a thermal magnetic circuit breaker works: the bimetal strip, the magnetic trip, and the curve that decides whether a fault takes milliseconds or minutes.
2026-07-02
7 min read
- 24
Why a GFCI Trips at 5 Milliamps: How Ground-Fault Protection Actually Reads the Wire
How does a GFCI work? It trips at 4–6 milliamps by comparing hot and neutral current, not by sensing a ground. A field guide to ground-fault protection and the human heart.
2026-06-27
7 min read
- 25
Three-Phase Power and the Square Root of 3: Where 1.732 Actually Comes From
Why three-phase power calculations use the square root of 3 (1.732): the geometry behind line-to-line voltage, and how to use it without memorizing it.
2026-06-27
7 min read
- 26
Residential Load Calculation: Why You Don't Add Up Every Appliance
A residential electrical load calculation never sums every nameplate watt. Learn how NEC demand factors and diversity let you size a service that's safe but not absurd.
2026-06-26
7 min read
- 27
Multiwire Branch Circuits: Why the Shared Neutral Can Carry Less Current — or Suddenly Carry More
How a multiwire branch circuit shares one neutral across two hots, why an open shared neutral overloads it, and what NEC 210.4 requires for safe wiring.
2026-06-26
7 min read
- 28
Available Fault Current and AIC Ratings: Why a Breaker Can Lose the One Fight It Was Built For
Available fault current is the number that decides whether a breaker clears a short circuit or explodes trying. Here's how to read it, calculate it, and match an AIC rating that holds.
2026-06-26
7 min read
- 29
Wire Temperature Ratings Explained: Why You Size to the 75°C Column With 90°C Wire
Wire temperature ratings 60/75/90°C confuse even seasoned electricians. Here's why your 90°C THHN gets sized to the 75°C column—and when the hot number is legal.
2026-06-24
7 min read
- 30
Why Loose Electrical Connections Start Fires: Torque, Heat, and NEC 110.14
Why electrical connection torque specs matter more than gut feel: how a loose terminal builds heat and starts a fire, and what NEC 110.14(D) now requires.
2026-06-23
7 min read
- 31
The 80% Breaker Rule: Why a Continuous Load Needs 125% Wire and Breaker
The continuous load 125% rule explained: why a 20A breaker only carries 16A of continuous load, what NEC 210.20 means, and how to size for heat.
2026-06-23
7 min read
- 32
Grounding vs. Bonding: The Difference That Trips Up Even Good Electricians
Understand the difference between grounding and bonding in the NEC—why the earth doesn't clear a fault, what the bonding jumper actually does, and where neutral and ground meet.
2026-06-22
7 min read
- 33
Conduit Fill Calculation: Why You Can Only Fill a Pipe 40% Full
A clear guide to the conduit fill calculation and the NEC 40 percent rule — why a pipe that looks half empty is already full, plus the jam ratio that ruins pulls.
2026-06-22
7 min read
- 34
Derating Wire for Heat and Bundling: Why the Ampacity Table Isn't the Final Answer
Conductor derating explained: how ambient heat and crowded conduit shrink a wire's real ampacity, why you start at the 90°C column, and how to size it right.
2026-06-20
7 min read
- 35
Voltage Drop Calculator: Sizing Conductors So You Pass the First Time
Undersized conductors fail inspection and starve equipment. Here's the NEC voltage-drop math, the 3% rule, and how to size a run right the first time — in seconds, offline.
2026-06-11
6 min read
- 36
The Calculation Habit That Separates a Clean Job From a Callback
A field workflow for electricians: when to run the numbers, what to calculate before you leave the truck, and how a calculation habit prevents costly callbacks.
2026-06-11
8 min read
- 37
One App Instead of a Drawer: The Offline Electrician Calculator
Conduit bending, ampacity, box fill, Ohm's law — most electricians own a half-dozen single-trick paid apps. Here's the case for one offline tool that does all of it.
2026-06-11
5 min read
- 38
EMT, IMC, or Rigid: Choosing the Right Conduit
A decision guide to EMT vs IMC vs rigid metal conduit: how wall thickness, connection method, and location decide which raceway belongs on your job.
2026-06-07
8 min read
- 39
Sizing a Feeder to a Detached Garage 150 Feet Away
Walk through feeding a detached sub-panel: how ampacity, voltage drop over distance, and the four-wire grounding rule all decide the conductor for a long feeder.
2026-06-03
9 min read
- 40
Reading the Ampacity Table: A Beginner's Guide to 310.16
A plain-English primer on reading NEC Table 310.16 ampacity: what the three temperature columns mean and the termination rule that decides which one you actually use.
2026-05-29
8 min read
- 41
The Box Fill Calculation Everyone Gets Slightly Wrong
Box fill seems simple until you count it. Here's how a NEC 314.16 box fill calculation actually works, and the counting mistakes that lead to overfilled boxes.
2026-05-24
8 min read
- 42
Why a Wire Has Resistance, and Why Aluminum Needs to Be Bigger
A field guide to conductor resistance: why length and material change voltage drop and ampacity, and why aluminum wire is sized larger than copper for the same load.
2026-05-19
8 min read
- 43
The Voltage Drop Myth: Is 3% Actually in the Code?
Most electricians cite a voltage drop code requirement that isn't quite what they think. Here's what the NEC actually says about the 3% rule, and why it still matters.
2026-05-13
8 min read
- 44
How to Bend a Conduit Offset That Actually Lands
A practical guide to bending a conduit offset: the multiplier, shrink, and the small mistakes that turn one clean offset into a scrap piece on the floor.
2026-05-07
8 min read