Free Online Calculators — Finance, Math & Construction

Tubing Capacity Calculator

Calculate tubing capacity in bbl/ft, gal/ft, L/m, and total fluid volume from outside diameter, wall thickness, and string length.

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Annular Capacity Calculator

Calculate annular capacity and volume in bbl/ft, gal/ft, ft/bbl, liters, and stepped multi-interval wells.

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Age Calculator — Exact Age, Days & Next Birthday

Calculate exact calendar age in years, months and days, total elapsed days, hours and minutes, age on any date, and the next birthday.

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Body Fat Calculator — Navy Method & Lean Mass

Enter height, neck and waist (plus hip for the female equation) to see the estimate immediately; optionally add weight for fat mass, lean mass and a target scenario.

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Calorie Calculator — Daily Calorie Intake & Macros

Calculate BMR, TDEE, and daily calories for weight loss, maintenance, or muscle gain in metric or imperial units, with a visual macro breakdown.

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Concrete Calculator — Cubic Yards, Bags & Cost

Enter a slab, footing, column, stair, or mixed pour and see concrete cubic yards immediately, then refine waste, truck loads, bags, and cost.

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Free Date Calculator — Days Between Dates & Age Calculator

Calculate days between dates, add or subtract days, or find an exact age with weekend controls, clear steps, and instant visual results.

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Ovulation Calculator — Fertile Window & Cycle Calendar

Estimate ovulation, fertile-window and next-period dates from an average cycle or a variable cycle-length range, with a visual calendar and three-cycle forecast.

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Pregnancy Due Date Calculator — Weeks, IVF & Timeline

Estimate your due date and gestational age from last period, conception, IVF transfer, ultrasound age, or a known clinical due date, with a week-by-week visual timeline.

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Random Number Generator — One Number or a Unique Sample

Generate one number from a clearly labelled inclusive range, or create, sort, copy and download a larger random sample.

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Rectangular Tube Load Calculator — RHS & SHS Beam

Check RHS or SHS bending stress, deflection and estimated load capacity for steel, stainless steel or aluminum with simple, fixed or cantilever supports.

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