Guides for people who measure things
Practical writing on shipping, dimensional weight, volume math, and the surprising amount of geometry hidden inside everyday decisions.
Dimensional Weight Explained: How FedEx, UPS, USPS, and DHL Calculate It
A clear, complete explanation of dimensional weight: what it is, why carriers charge it, and the exact formulas used by FedEx, UPS, USPS, and DHL in 2026.
How to Read a FedEx Shipping Label (And What the DIM Weight Means)
How to read a FedEx shipping label — and why the weight printed on it isn’t always the weight you’re billed. Includes FedEx’s 139 DIM formula and 2026 residential surcharges.
UPS vs FedEx: Which Has Better Dimensional Weight Rules in 2026?
UPS vs FedEx from their 2026 rate guides: 139 vs 166 divisors, identical size thresholds, packaging differences and every 2026 surcharge amount side by side.
International Shipping Dim Weight: Why the 5000 Divisor Matters
The 5,000 cm³/kg divisor FedEx and UPS use in metric is effectively the same as the 139 in³/lb US divisor. Here’s the conversion, where the small differences come from, and how to calculate it.
How to Avoid Oversize Shipping Fees: The 48, 96, 130 and 165-Inch Lines
The size lines that trigger FedEx and UPS Additional Handling, Oversize/Large Package and maximum limits, and USPS size limits — from the carriers’ own documents — and how to design boxes that stay under them.
Girth in Shipping: What It Is and Why It Costs You Money
Girth is the distance around a package perpendicular to its longest side. Learn the formula, why carriers use it, and how to measure your boxes correctly.
How to Calculate Aquarium Volume (And Why It Matters for Your Fish)
Step-by-step guide to calculating fish tank volume in gallons and liters, including how to handle substrate displacement, stocking density, and medication dosing.
How Much Soil for a Raised Garden Bed: A Calculator-Backed Guide
How to calculate soil volume for a raised garden bed in cubic yards and bags, including settling allowances, soil mix recommendations, and bulk vs bagged break-even.
Swimming Pool Volume: Why Your Pool Store's Estimate Is Probably Wrong
Calculate your swimming pool's exact volume in gallons or liters, with formulas for rectangular, oval, and freeform pools, and a chlorine dosing reference table.
Will My Fridge Fit Through the Doorway? The Tilt Math Explained
How to measure a doorway and an appliance to know if a fridge, sofa, or washer will fit through. Includes the tilt-diagonal formula and tips for tight clearances.
How to Estimate Cubic Feet for a Move (Without Hiring a Mover)
Calculate the total cubic feet of your move to size a truck correctly. Includes room-by-room estimates, furniture sizes, and U-Haul/Penske truck capacities.
The Volume of a Rectangular Prism: A Complete Guide
Comprehensive explanation of how to calculate the volume of a rectangular prism, including the formula derivation, worked examples, and common student mistakes.
Cubic Centimeters vs Milliliters: Are They the Same Thing?
Cubic centimeters (cm³) and milliliters (mL) are exactly equal — here's the historical reason, when each is used, and why the confusion exists.
How to Convert Cubic Feet to Gallons (And Why It's Trickier Than You Think)
Convert cubic feet to gallons with the 7.48 conversion factor, plus US vs UK gallon differences, common errors, and a full reference table.
Surface Area vs Volume: The Difference That Confuses Everyone
Surface area and volume measure different things in different units. Here's the precise difference, with worked examples and practical applications.
The Box Diagonal Formula: Pythagoras in 3D
Calculate the space diagonal of a rectangular box using the 3D Pythagorean theorem. With derivation, worked examples, and practical applications for fitting things into boxes.
Amazon FBA Dimensional Weight: The Complete 2026 Guide
Amazon’s 2026 FBA rules from Seller Central: the 139 dimensional weight divisor, which tiers use it, the new Small Bulky tier, 2026 fulfillment fees and Amazon’s own examples.
Pallet Volume Calculation for Freight: A Warehouse Operator's Guide
How to calculate pallet volume for LTL freight, dimensional weight rules, density classification, and the freight class system every operator should know.
3PL Dim Weight Negotiation: How to Get a Better Divisor
Strategies for negotiating dimensional weight divisors with 3PLs and carriers, including realistic targets, volume thresholds, and negotiation tactics that work in 2026.
Storage Unit Sizing: How to Calculate What Actually Fits
How to size a storage unit correctly — calculate cubic feet, compare standard unit sizes, and estimate what fits in a 5x10, 10x10, and 10x20 unit.