The math you do standing next to the work.
Cut angles, conduit bends, sling loads, tank fills. Field calculators for carpenters, electricians, riggers, and haulers who need the number, not a spreadsheet.
The jobsite doesn't wait
while you find a spreadsheet.
There's a particular kind of math that only exists standing next to the work. One hand holding a tape, the other holding a phone, gloves on, sun on the screen, and a number you need in the next thirty seconds because the saw is running and the crane operator is looking at you. It isn't hard math. Most of it is one line of trigonometry. But it has to be right, it has to be fast, and it has to run on the inputs you can actually measure from where you're standing.
The chart, before you need the tool
The trades solved this a century ago with memorized constants and printed tables. Multipliers for common bend angles. Cheat charts for crown corners. Load tables laminated to the gang box lid. That system works right up until the job leaves the table's assumptions: the corner that isn't square, the sling angle that isn't in the chart, the tank lying on its side where a half-wet stick is nowhere near a half-full tank. Then people guess. Usually they guess conservative, which costs material. Sometimes they guess wrong in the other direction, which costs a lot more than material.
So here is the laminated card, grouped by trade, every constant pulled from the same math the tools run. Each group ends with the tool that handles the case the chart can't.
Bend an offset and the conduit gets effectively shorter. Every electrician knows shrink exists; the popular pocket references still manage to leave it out of the saddle instructions. Forget to add it back and your bend lands shy of the obstruction every single time.
| Bend angle | Mark multiplier | Shrink per inch of rise | Reach for it on |
|---|---|---|---|
| 10° | 5.759 | 0.088 in | Long, shallow runs |
| 22.5° | 2.613 | 0.199 in | Tight boxes, low shrink |
| 30° | 2.0 | 0.268 in | The everyday default |
| 45° | 1.414 | 0.414 in | Steep clears, big obstructions |
| 60° | 1.155 | 0.577 in | Maximum rise, short run |
More crown molding gets scrapped over one convention than over any saw problem. A 38° crown sits 38 degrees off the wall, not the ceiling. Get the reference plane backwards and both compound angles come out wrong together, which makes the error hard to spot until the corner won't close. And the corner itself is rarely square: framing lumber crowns, drywall builds up in layers, and a real inside corner runs 88 to 92 degrees. The printed cheat chart assumes 90 anyway.
| Crown setting | The convention |
|---|---|
| Spring-angle presets | 38°, 45°, 52°, or custom |
| Reference plane | The wall, not the ceiling |
| Corner input | The corner you measured; 88° to 92° is normal |
The same trade owns the other blind spot: a circular blade cuts farther at the surface than it does at depth, and the run-out past your line grows with every inch you drop the blade.
| Cut depth, 24 in blade | Overrun at the surface |
|---|---|
| 4 in | 8.9 in |
| 6 in | 10.4 in |
| 8 in | 11.3 in |
Almost every published sling-tension formula wants degrees from horizontal. Nobody on a rigging crew carries a protractor. What you can measure with the tape already in your pocket is vertical height and leg length, and the trig runs fine off those two numbers alone. The factors below are listed by angle because that is how the charts print them; Legload derives the angle for you from the two tape measurements.
| Sling angle | Tension factor | Legload flag |
|---|---|---|
| 60° | 1.155 | No flag |
| 45° | 1.414 | Amber. The caution zone starts here |
| 30° | 2.0 | Amber. One degree lower reads red |
Check the answer against rated WLL with a qualified person before every lift.
Legload runs the trig from height and leg lengthA 24-inch trailer deck with 8-foot ramps loads at about 14.5 degrees, which is already steeper than the approach angle of most passenger cars. That's the geometry behind every scraped bumper and every high-centered mower deck at the transition point.
| Ramp length, 24 in deck | Loading angle |
|---|---|
| 6 ft | 19.5° |
| 8 ft | 14.5° |
| 10 ft | 11.5° |
The last entry on the card is the one a straight-sided mental model butchers: a tank lying on its side does not fill in proportion to the stick.
| Stick reading, horizontal tank | Tank holds |
|---|---|
| 1/4 wet | 19.6% of capacity |
| 1/2 wet | 50% of capacity |
| 3/4 wet | 80.4% of capacity |
Four numbers the field runs on
45° offset multiplier
Distance between bend marks per inch of rise. The book says 1.414; half the field rounds it to 1.4 and eats the difference.
sling tension at 30°
Drop a two-leg sling to 30 degrees from horizontal and each leg carries double its share of the load. The load didn't change. The angle did.
blade overrun, 24″ at 6″ deep
A round blade cutting 6 inches deep runs past your line by more than 10 inches at the surface. Chord geometry, not operator error.
tank volume at a quarter stick
A horizontal tank with the stick wet a quarter of the way up holds under a fifth of its capacity. The fat middle lies to you in both directions.
When to reach for which one
Every one of them follows the same house rules. The inputs are the measurements you already have, in the units the trade uses, fractional inches included. The assumptions are printed on the page, not buried in a footnote. The result is the biggest thing on screen. And none of it replaces the code book, the load chart, or the qualified person who signs off on the lift. These are first-pass field numbers. Verify anything that can hurt somebody.
A wrong number in an office costs a revision. A wrong number twenty feet up a ladder, under a suspended load, or one saw pass into a finished slab costs something you can't revise. That is the bar the six calculators on this shelf are held to: inputs a tape can take, assumptions in plain sight, an answer you can read at arm's length in daylight, and no login between you and the number. Memorize the chart if you like. The tools are for the day the job ignores it.
Field Math
Know how far your blade runs past the line — before the first cut.
A round blade always cuts past your line. On a 24-inch blade going 6 inches deep that overrun is more than ten inches, and most cutters eyeball it. Overcut runs the geometry off the inputs you actually think in — blade diameter and cut depth, in fractional inches — and draws the side profile so you can see the run-out before you commit. Forward gives you the overcut, Bevel adds a tilt angle, and Reverse turns a hard clearance limit into the deepest single-pass cut you can safely make. One screen, no login, built for a phone in a dusty glove.
Try it 02Cut crown molding right the first time.
Compound-angle trig is non-obvious and real corners are never exactly 90 degrees, so the printed paper cheat-charts carpenters still carry only get you so far. Crownset is the digital version: tap a crown spring-angle preset (38, 45, 52, or custom), type your measured wall corner, and read the exact miter and bevel to dial on the saw. A built-in cross-section diagram settles the spring-angle convention question once and for all (it's measured from the wall, not the ceiling, the single most common source of bad cuts). Inside and outside corner results show at the same time so a whole-room run never makes you re-toggle, and a saw-orientation diagram tells you which face goes down and which way to swing. Free, mobile-first, and works offline after the first load.
Try it 03Read the stick, get the gallons.
Lay a fuel tank on its side and a half-wet stick is nowhere near a half-full tank — the fat middle holds far more than the curved ends. Dipfill runs the exact circular-segment math off the three numbers you actually measure: tank diameter (never radius), length, and how far up the stick is wet. It hands back gallons remaining, percent full, and the one number almost no tool surfaces — gallons to fill, the figure you call in to order. Switch to litres for metric work. No login, no chart, big numbers and big touch targets for a phone at tank-side in a dusty glove.
Try it 04Tension per sling leg, from a tape measure — not a protractor.
Sling tension climbs silently as the angle drops: at 30° from horizontal each leg carries double the share of the load, and every other free web calculator forces a degrees-from-horizontal number a field rigger can't measure without a protractor. Legload takes the height and leg-length measurements you already have on your tape and returns tension per leg, the tension factor, and the derived angle instantly — paired with a live SVG geometry diagram and red/amber danger warnings at the 30° and 45° breakpoints. Nothing to set up, and no vendor upsell waiting at the end. Rule-of-thumb field math built for a gloved phone between lifts; verify against rated WLL with a qualified person before every lift.
Try it 05The shrink number Ugly's leaves out — front and center, in one glance.
Offset and 3-point saddle shrink is closed-form math every electrician eyeballs, mis-remembers, or hunts for in a table on the job — and Ugly's famously omits the shrink step from its 3-point saddle how-to entirely. Bendmark puts it front and center: pick a real trade angle (10, 22.5, 30, 45, or 60°), punch in the rise (and obstruction width for saddles), and instantly read mark spacing plus the shrink to add back, with the shrink value as the largest thing on screen. One distraction-free page flows bend type to marks to shrink — offset and saddle unified, no login, no page jump, no affiliate chrome. Editable take-up/deduct, fractional-inch to the nearest 1/16", high-contrast for a phone in bright sunlight. Verify against your own bender before the cut.
Try it 06The ramp length you need — and whether you'll drag your belly getting up it.
Two numbers every hauler eyeballs and gets wrong: how long a ramp has to be for a safe loading angle, and whether a low car, mower deck, or lowboy load will high-center at the transition. Rampset solves both on one screen. Enter deck or bed height and pick a load-type preset (car, ATV/UTV, mower, lowboy) — or reverse-solve the angle from a ramp you already own — and read the required length live. Add ground clearance and wheelbase and it computes the breakover angle and surfaces a conservative should-clear / will-likely-drag verdict as a headline result, with a live side-profile diagram. No login, no vendor upsell, works offline after first load. Built for a phone next to the trailer with a tape measure in hand; treat the breakover check as a guide, not a guarantee.
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