PhDino Calc 95 — Free Engineering Calculators
PhDino is a free collection of 97 engineering calculators across 12 fields: structural, mechanical, electrical, and geotechnical engineering, plus civil and construction materials, chemistry, solar and renewable energy, manufacturing and machining, aerospace, biomedical, motorsport, and digital logic. The calculators run entirely in your browser — no account, nothing to install, and what you type is never sent to a server.
A few calculators to start with: Beam Deflection, Ohm's Law, Column Buckling, Concrete Volume, Solar Array Sizing, BMI Calculator. Or browse all 97 by field below.
How each calculator works
Every calculator does three things at once: it computes results in real time as you type (no "calculate" button), it draws a live schematic diagram that updates with your inputs, and it links to a plain-English guide explaining the formula, the variables, the assumptions, and the standard it comes from (AISC, ACI, NEC, ASHRAE, and so on). You can switch any field between imperial and metric, or override one field's unit on its own. Results you keep go into a Notebook that exports to a branded PDF.
How the numbers are checked
Every calculator is tested automatically each time the site is built, against expected answers worked out a different way (through SI units, from closed-form expressions, or from published constants). A calculator that fails cannot be published. Where a calculator is a simplification or a rule of thumb, its page says so at the top. The full method, and a public log of corrections, is on the Methodology page.
Project guides
11 step-by-step guides chain several calculators together for a real task — building a deck, sizing a home backup generator, wiring a subpanel, prepping a lab solution, sizing an off-grid solar system, and more — passing values from one step to the next so you're not re-typing numbers.
- Build a Deck — Check the joists and beam for stiffness and size the footings for a backyard deck, following the load from the deck boards down to the soil.
- Build a Retaining Wall — Check the ground under and around a retaining wall before sizing the wall itself, so you're not designing a wall on soil that can't hold it.
- Size a Home Backup Generator — Work out how many watts a backup generator needs to run and to start your loads, convert that to amps, then check the wiring between the generator and your panel.
- Wire a Subpanel — Work out the current an individual load draws, then size the feeder that runs from the main panel out to a garage or workshop subpanel so the far end still gets full voltage.
- Pour a Concrete Patio or Slab — Work out how much concrete and gravel to order, how to batch the concrete if you mix it yourself, and how much rebar to place, in the order you'd actually plan the pour.
- Prepare a Lab Solution from Scratch — Weigh out a compound to make a concentrated stock, then dilute it down (in one stage or two) to the working concentration you actually need.
- Go Off-Grid: Size a Solar Power System — Size the panels, batteries, charge controller and inverter for an off-grid solar setup, in the order a real system gets designed.
- Machine a Part from Raw Stock — Weigh your starting stock, dial in the spindle speed and feed for the drill you'll use, then estimate the cycle time of the drilling operation.
- Plan an Orbital Maneuver — Work out the delta-v an orbital transfer needs, then how much of your rocket's mass has to be propellant to deliver it, and how that changes with the engine.
- Set Up a Race Car's Corner Balance — Scale the car's four corners, then use those real weights for weight-transfer and spring-rate setup instead of guessed numbers.
- Design a Synchronous Circuit's Timing — Work out your critical path delay, pick a clock period that respects it, then confirm the flip-flops on that path actually meet setup and hold.
All 97 calculators
Structural
- Beam Deflection — Calculate deflection of beams under uniform loads
- Column Buckling — Axial capacity of a steel column, from Euler buckling with the AISC inelastic reduction for stocky columns
- Concrete Strength — Estimate concrete strength development
- Footing Design — Size a square spread footing from the column load and the allowable soil pressure
- Moment Distribution — Support and span bending moments of a two-span continuous beam under uniform loads (three-moment equation)
- Steel Connection — Design bolted steel connections
- Stress Concentration — Calculate stress concentration factors
- Truss Analysis — Screening check of one steel truss member: tension and compression capacity against an applied axial load
Mechanical
- Bearing Stress — Calculate bearing stress on surfaces
- Fatigue Analysis — Goodman fatigue safety factor for a fluctuating stress, with a simplified endurance limit of half the ultimate strength
- Gear Ratio — Calculate gear ratios and speeds
- HVAC Cooling — Calculate HVAC cooling load
- Motor Sizing — Choose a standard motor rating for a mechanical load, allowing for a service factor and drive losses
- Pipe Flow — Calculate pipe flow parameters
- Torsion — Calculate torsional stresses
Electrical
- Cable Sizing — Smallest copper conductor that keeps voltage drop within an allowed percentage over a given run (voltage drop only, not ampacity)
- Ohm's Law — Basic electrical calculations (V=IR)
- Power Calculation — Real, reactive and apparent power of a single-phase or balanced three-phase load from voltage, current and power factor
- Transformer Sizing — Choose a standard single-phase transformer rating for a load, and find the primary and secondary full-load currents
- Voltage Drop — Calculate voltage drop in conductors
Geotechnical
- Consolidation Settlement — Calculate primary consolidation settlement
- Pile Capacity — Ultimate and allowable capacity of a single round pile from unit skin friction and unit end bearing
- Retaining Wall — Active earth pressure on a retaining wall (Rankine), the overturning moment it causes, and a rule-of-thumb base width
- Slope Stability — Simplified slope safety factor
- Soil Bearing Capacity — Ultimate and allowable bearing capacity of a strip footing (Terzaghi-form equation with Prandtl–Reissner and Hansen factors)
Civil / Construction Materials
- Asphalt Thickness — Simplified planning estimate for driveway/parking-lot asphalt + base thickness
- Concrete Mix Design — Estimate cement, sand, gravel, and water for a volume-ratio concrete mix
- Concrete Volume — Work out how much concrete a slab or footing needs, in the units ready-mix is sold by
- Culvert Flow — Full-flow capacity of a circular culvert using Manning's equation
- Excavation Volume — Cut volume and truck loads for hauling excavated soil off site
- Masonry Block Count — Estimate concrete block and mortar quantities for a wall
- Rebar Sizing — Estimate rebar count and weight for a two-way slab grid
- Soil Compaction Check — Compare a field density test against the lab Proctor maximum
- Stormwater Runoff — Peak runoff rate from a drainage area using the Rational Method
Chemistry
- Buffer Solution — pH of a buffer from the Henderson-Hasselbalch equation
- Ideal Gas Law — Solve PV = nRT for whichever of pressure, volume, moles, or temperature is left blank
- Molar Mass & Solution Prep — How many grams of a compound to weigh out for a target concentration and volume
- Molarity / Dilution — How much stock solution and water to combine for a target diluted concentration
- Percent Yield — Compare an actual reaction yield against the theoretical maximum
- pH Calculator — pH and pOH of a strong acid or base solution
- Reaction Half-Life — Half-life and remaining concentration for a first-order reaction
- Stoichiometry — Find the limiting reagent and product yield from a balanced equation
- Titration — Volume of base (or acid) needed to reach the equivalence point
Renewable Energy / Solar
- Battery Bank Sizing — Battery capacity needed to cover a daily energy need for a target number of backup days
- Charge Controller Sizing — Required current rating for a solar charge controller
- Inverter Sizing — Continuous and surge power ratings an inverter needs to cover a set of loads
- Net Metering Savings — Monthly bill savings and banked credit from a net-metered solar system
- Off-Grid Autonomy — How many days a battery bank can cover a daily energy need with no sun
- Panel Tilt Angle — A latitude-based starting point for fixed solar panel tilt angle
- Solar Array Sizing — How many solar panels it takes to cover a daily energy need
- Solar Payback Period — How many years it takes a solar installation to pay for itself
- Wind Turbine Output — Power a small wind turbine captures at a given wind speed, and the annual energy if that speed never changed
Manufacturing / Machining
- Bolt Circle Pattern — Angle and chord spacing between holes on a bolt circle
- CNC Speeds & Feeds — Spindle speed and feed rate for a milling or drilling operation
- Drilling Cycle Time — Machining time for a set of drilled holes at a given feed and speed
- Metal Stock Weight — Weight of a length of round, square, flat, or tube stock
- Press Brake Tonnage — Tonnage needed to air-bend a sheet metal part
- Sheet Metal Bend Allowance — Bend allowance and deduction for a flat-pattern layout
- Surface Finish Estimate — Theoretical surface roughness left by a turning feed and tool nose radius
- Tap Drill Size — Drill diameter to use before tapping a given thread
- Tolerance Stack-Up — Worst-case and statistical (RSS) stack-up of four toleranced dimensions
Aerospace
- Drag Equation — Aerodynamic drag force from airspeed, reference area, and drag coefficient
- Escape Velocity — Velocity needed to escape a body's gravity from a given altitude
- Hohmann Transfer Orbit — Delta-v budget for a two-burn transfer between circular orbits
- Lift Equation — Aerodynamic lift force from airspeed, wing area, and lift coefficient
- Mach Number — Mach number and local speed of sound at a given air temperature
- Orbital Velocity — Circular orbital velocity and period at a given altitude
- Rocket Equation — Solve Tsiolkovsky's rocket equation for whichever of Isp, mass, or delta-v is left blank
- Thrust-to-Weight Ratio — Whether a vehicle's engine(s) can lift it off the ground under its own thrust
- Wing Loading — Aircraft weight per unit of wing area
Biomedical / Clinical
- Anion Gap — Serum anion gap from basic metabolic panel electrolytes
- BMI Calculator — Body mass index from height and weight
- BMR & Caloric Needs — Basal metabolic rate and daily caloric needs using the Mifflin-St Jeor equation
- Body Surface Area — Estimated body surface area using the Mosteller formula
- Creatinine Clearance — Estimated creatinine clearance using the Cockcroft-Gault equation
- IV Drip Rate — Drip rate and flow rate for a gravity IV infusion
- Pediatric Dosage (Clark's Rule) — Scale an adult medication dose down to a child's weight using Clark's Rule
- Target Heart Rate Zones — Age-predicted maximum heart rate and a moderate-to-vigorous training zone
- Weight-Based Drug Dosage — Total dose from a patient's weight and a per-kilogram dosing rate
Motorsport
- Aerodynamic Downforce — Downforce generated at a given speed, frontal area, and downforce coefficient
- Braking Distance — Braking distance and total stopping distance including reaction time
- Corner Weight Balance — Front/rear, left/right, and cross-weight percentages from a car's four corner weights
- Fuel Load Strategy — Fuel needed for a race distance, its added weight, and pit stops required
- Gear Ratio & Top Speed — Theoretical top speed in a given gear at a target engine RPM
- Lap Time Delta — Estimated lap time change from a change in average lap speed
- Suspension Spring Rate — Wheel rate and ride frequency from a spring rate, motion ratio, and corner weight
- Tire Contact Patch — Estimated contact patch area and length from a tire's load and pressure
- Weight Transfer — Longitudinal weight transfer under braking or acceleration
Digital Logic / Computer Engineering
- Addressable Memory — How many locations an address bus width can address
- Bit Width & Parity — Minimum bits needed to represent a value, its population count, and parity
- Boolean Function Counter — How many truth table rows and possible functions exist for N boolean variables
- Clock Frequency & Duty Cycle — Clock frequency and high/low time from a clock period and duty cycle
- Flip-Flop Setup/Hold Margin — Setup and hold timing margin for a synchronous flip-flop-to-flip-flop path
- Half/Full Adder — Sum and carry-out for two bits plus an optional carry-in
- Karnaugh Map Position Finder — Row and column position of a minterm on a 4-variable Karnaugh map
- Logic Gate Propagation Delay — Total propagation delay through a combinational logic path and the clock frequency it implies
- Minterm Decoder — Decode a minterm number into its 4 variable (A, B, C, D) values
FAQ
Is PhDino free?
Yes. There is no charge and no account. The site is meant to be supported by advertising and by book links that earn a small commission (see the Affiliate disclosure), never by selling your data.
Do I need an account?
No — no sign-up, no login.
Is my data private?
The calculators run in your browser: the numbers you enter and the results you get are not sent to a server. The site does use a cookie-consent tool, and may show advertising, which can set cookies once you agree; see the Privacy Policy for the details.
Is it accurate enough for real engineering work?
It is accurate as an educational and screening tool, and each calculator is tested against independent reference values. It is not a substitute for a licensed engineer or the official code text, and several calculators are deliberate simplifications that say so on their page. The biomedical calculators are not for clinical use.
Where do the formulas and explanations come from?
From standard, published engineering relationships and the named standards bodies. The text was written with the help of an AI assistant under the maintainer's direction, and no textbook text is copied. The Methodology page explains how each calculator is verified.
Who makes it?
PhDino is built and maintained by one independent developer. The About page says who, and the Contact page is the way to report an error or make a suggestion.