Every Rigging Calc.
One App.
Professional rigging calculator for every lift
Sling tensions, crane capacity, load weight, centre of gravity and drift — built for riggers, crane operators and lift supervisors. 100% offline, no signal required.
Key Features
Everything a rigger needs before the load leaves the ground
Sling Load & Tension
Tension per leg for 1–4 leg slings. Enter the sling angle directly or let the app derive it from height and length. Instant warnings when angles drop below 30° and tension doubles.
Load Weight Estimator
Estimate load weight from shape and material — plates, pipes, cylinders, blocks and I-beams in steel, aluminium, concrete, timber and more.
Center of Gravity
Two-point picks on asymmetric loads. See the share of the load at each pick point and where the centre of gravity sits before you rig it.
Crane Capacity Check
Load weight plus rigging gear plus hook block against the chart capacity. Utilisation percentage and safety status at a glance.
Drift / Headroom
Enter hook height and sling lengths to get headroom above the load. Know your available height before the lift, not during it.
Reference Charts & Guides
WLL tables for shackles, wire rope, chain slings, web slings and eyebolts, plus crane hand signals, hitch types and a rigging unit converter.
How It Works
Three steps from load weight to safe sling tension
Enter Your Load
Type the load weight in pounds or kilograms — or estimate it from shape and material with the Load Weight Estimator.
Set Sling Angle & Legs
Pick 1 to 4 legs, then enter the horizontal sling angle or the sling length and vertical height.
Get Safe Tensions
Read tension per leg, angle factor, effective legs and the safety status — with a warning if the angle is too tight.
Sling Angle Changes Everything
A 1,000 lb load on a two-leg sling. Same load, same slings — only the horizontal sling angle changes. This is the arithmetic RigCalc Pro runs before the load leaves the ground.
| Sling angle | Angle factor | Tension per leg |
|---|---|---|
| 90° | 1.000 × | 500 lb |
| 60° | 1.155 × | 577 lb |
| 45° | 1.414 × | 707 lb |
| 30° | 2.000 × | 1,000 lb |
At 30° each leg carries the entire load — twice what it carries at 90°. The app flags angles below 30° and shows the severity as you type, so a tight pick never gets rigged on a guess.
ASME B30.9 & OSHA 1926.251
Tension, angle factor and capacity formulas follow published rigging practice.
No brand lock-in
Enter any shackle, sling or crane chart. Nothing is tied to one manufacturer catalogue.
Reference, not authority
A planning aid for trained and qualified rigging personnel — always verify against the manufacturer’s tag.
Why RigCalc Pro
Built for the conditions rigging actually happens in
100% Offline
Every calculator and chart runs on the device. Basements, structures, remote sites — no signal needed.
Available Worldwide
Listed in 36 languages across 175 App Store regions, with both imperial and metric units.
Glove-Friendly UI
Large touch targets and a high-contrast dark interface that stays readable in direct sun.
Angle Warnings Built In
Severity is shown as you type. Tight angles are flagged before they become a tension problem.
Calculation History
Recent picks are saved on the device so a figure can be checked again later. Pro removes the limit.
Free Sling Calculator
The Sling Load & Tension Calculator is free and unlimited — no account, no sign-up, no trial needed.
Frequently Asked Questions
Does RigCalc Pro work offline?
Yes. Every calculation engine and every reference chart runs locally on your iPhone, so the app works in a basement, inside a structure, or anywhere else the signal drops.
What's included for free and what needs Pro?
The Sling Load & Tension Calculator is free and unlimited, along with the hitch types guide, unit converter, a starter set of crane hand signals, and your recent calculation history. Pro unlocks the Load Weight Estimator, Center of Gravity, Crane Capacity Check, Drift / Headroom, the complete WLL chart library, the full hand-signal set, and unlimited history.
How does the subscription work?
RigCalc Pro is free to download. Pro is available weekly ($1.99 after a 1-week free trial) or annually ($19.99 after a 1-month free trial). Subscriptions renew automatically through your Apple account and can be cancelled any time in App Store subscription settings.
Which standards do the calculations follow?
Sling tension, angle factors and capacity figures follow the formulas and practice described in ASME B30.9 and OSHA 1926.251. The app is a planning aid for trained and qualified rigging personnel — always verify against the manufacturer’s tag, the load chart for your specific crane configuration, and your site’s lift plan before making a pick.
Imperial or metric?
Both. Enter loads in pounds or kilograms and switch units anywhere in the app; the built-in converter also handles length, force and mass conversions used in rigging work.
Contact Us
Questions, a chart you need added, or a bug to report? We read every message.