The free rigging calculator at buildrightacademy.us/tools/rigging-calculator runs six field-ready calculations — sling tension per leg, a load angle factor table, a sling WLL/hitch check, top-block or gin-pole sheave load, capstan hoist pull, and a simple center of gravity — with no login and no cost. It's built for the numbers a tower tech, climber or foreman actually needs mid-lift, in ft/lb or metric. The only thing behind a free account is the full multi-point Rigging Plan Calculator that builds a complete A10.48-style plan.
What's actually free, and what needs an account?
Everything on the main rigging calculator page works instantly with zero signup:
- Sling angle → tension per leg (2, 3 or 4-leg bridles)
- The load angle factor table (90° down to 15°)
- Sling WLL / hitch check (vertical, choker, basket)
- Top-block / gin-pole sheave load
- Capstan hoist pull
- A simple single-axis center of gravity
Creating a free account — email/password or Google, no credit card — unlocks the full Rigging Plan Calculator, which runs the complete lift path (six rigging configurations, obstruction clearance, wind load, anchorage demand, required A10.48 plan Class) and generates a printable PDF plan. It's free while BuildRight builds the product out further.
Who is this calculator for?
Tower techs and climbers checking a sling or hoist number before a pick, foremen double-checking a crew's rigging plan on a tablet, and safety managers who want a quick second opinion on a number someone radioed down. It's a field tool, not a training course — it assists a qualified or competent rigger, it doesn't make someone into one.
Station-by-station: what each calculator does
01 — Sling Angle → Tension per Leg. Enter total load, number of legs (1–4) and the sling angle from horizontal on a slider (15°–90°); it returns tension per leg and the load angle factor instantly. 3- and 4-leg bridles are automatically treated as 2 effective legs carrying the load, the standard conservative assumption.
02 — Load Angle Factor Table. A reference table, 90° down to 15°, showing the multiplier (1 ÷ sin(angle)) and what it does to a 1,000 lb load at each angle — useful for a quick gut-check without typing your own numbers in.
03 — Sling WLL / Hitch Check. Enter the sling's tagged WLL, the hitch type (vertical = 100% of tag, choker = 75%, basket = 200%), and the required leg tension; it returns effective capacity and a clear pass/fail.
04 — Top Block / Gin-Pole Sheave Load. Enter line tension and the included angle between the two rope legs crossing the sheave (0°–180°); it returns the resultant force the block, sling and shackle have to be rated for — which is up to 2× the line tension at a 0° included angle, not the line tension itself.
05 — Capstan Hoist Pull. Enter the load on the line, how many sheaves the rope passes before the capstan, and the sheave bearing type (steel roller, bronze bushing, plain bushing); it returns the required capstan pull after friction losses.
Recommended certification
Basic Rigging Principles on Communication Structures
$95 · ~4.5h online · certificate issued same day · valid 2 years
Also read: Monopole Collar Ring Mount Installation: New Video for Tower Safety · Dehydration Emergency on Rockford Tower Highlights Critical Safety
06 — Simple Center of Gravity. Enter weight and distance-from-reference for 2–4 point loads; it returns total weight and the center of gravity along that axis — a quick balance-point check for a spreader bar or multi-point pick.
Every station runs the same formulas as the full Rigging Plan Calculator — this page is the free, instant front end to the same calculation library.
What units does it support?
A toggle at the top switches the whole page between ft/lb (imperial) and m/kg (metric) — every station recalculates in the selected units, so there's no manual conversion mid-lift.
How is this different from the full Rigging Plan Calculator?
The free calculator answers single-point questions — "what's the tension on this leg right now." The full Rigging Plan Calculator (free account required) answers the plan-level question — it runs the entire lift path across multiple configurations (gin pole, heel block, trolley systems), checks obstruction clearance along the way, factors in wind on the load, determines the anchorage demand, determines the required A10.48 Construction Plan Class, and outputs a printable, sign-off-ready PDF. Think of this page as the pocket calculator and that one as the full plan.
FAQ
Is the BuildRight rigging calculator really free?
Yes. All six calculators on the rigging calculator page work instantly with no account and no cost. A free account additionally unlocks the full Rigging Plan Calculator.
Do I need to create an account to use the rigging calculator?
No — not for the instant calculators on the main page. An account is only needed for the full multi-point Rigging Plan Calculator with obstruction clearance and a printable PDF.
Does this rigging calculator work in metric?
Yes. A unit toggle switches every station between ft/lb and m/kg.
Can I use the rigging calculator for a 3- or 4-leg bridle?
Yes — select 3 or 4 legs in station 01. The calculator applies the standard conservative assumption that only 2 legs actually carry the load, the same assumption used in the full Rigging Plan Calculator.
Is this an OSHA-certified rigging calculator?
No. It's not an OSHA-certified or OSHA-approved product and doesn't issue any certification. It follows engineering methods consistent with ANSI/ASSP A10.48 and ASME B30.9, and it's meant to assist a qualified or competent rigger, not replace one.
What's the difference between this and the full Rigging Plan Calculator?
This page handles single-point field checks — sling tension, block load, capstan pull, WLL, CoG — instantly and for free. The full Rigging Plan Calculator (free account) runs the entire lift path, checks obstructions and anchorage, determines the required A10.48 plan Class, and generates a printable plan.
