Tools
Config-driven calculators and helpers—each tool doubles as an explainer page for search and sharing. Jump into a subject hub or scroll the full catalog.
By subject
Same grouping as your curriculum—e.g. chemistry calculators in one place.
All tools
Alphabetical list of published utilities Showing 145–192 of 564.
- formula calculator
Dilution calculator
Solve C₁V₁ = C₂V₂ for any missing concentration or volume (consistent units).
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Dimensional analysis (speed)
km/h ↔ m/s using exact factor 1/3.6.
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Discount calculator
Sale price from list price and % off.
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Discrete random variable calculator
E[X] and Var(X) from a PMF table.
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Displacement (constant a)
s = ut + ½at².
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Distance (coordinate)
Distance between (x1,y1) and (x2,y2).
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Distance (uniform speed)
Distance ≈ |v| t when speed is constant on a straight path.
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Divisibility checker
Does divisor divide dividend (integer sense)?
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DNA complement
Watson–Crick complement.
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DNA molecular weight (ss approx)
Approximate single-strand DNA mass.
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DNA sequence analyzer
Length, base counts, GC%.
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DNA to RNA transcription
T→U on cleaned coding-strand sequence.
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Doppler effect (sound)
Classic 1D cases for source or observer motion.
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Double integral calculator
∬ on a rectangle; f(x) or f(x,y).
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Doubling time
t_d = ln(2)/r for exponential growth.
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Drug dose (mg/kg)
Mass dose from mg/kg and body weight.
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ECG intervals (reference)
Typical adult rest intervals.
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Echo time
Round-trip time t = 2d/v.
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Ecological footprint (note)
Why full calculators need external factors.
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Effective nuclear charge calculator
Z_eff = Z − σ with screening σ you supply (e.g. from Slater rules).
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Efficiency
η = (useful output / total input) × 100%.
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Efficiency (systems)
η = (useful output / total input) × 100%.
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Elastic / inelastic collision solver
Same 1D solver with mode selection.
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Electrical energy
E = Pt or E = VIt.
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Electric current from charge
Average I = ΔQ/Δt.
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Electric field (point charge)
|E| = k|Q|/r².
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Electric potential (point charge)
V = kQ/r with V(∞) = 0.
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Electrolysis mass calculator
Mass deposited or dissolved: m = (Q·M)/(n·F) with Q in coulombs.
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Electron configuration lookup
Ground-state configuration string for Z = 1–118 (teaching data).
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Electron shell summary
K/L/M… occupancy from atomic number.
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Electron transfer (moles e⁻)
Moles of electrons from |ΔOS| × moles of atoms.
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Element comparison
Side-by-side mass, EN, radius, configuration for two elements.
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Element property finder
Look up symbol, Z, mass, and configuration snippet.
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EMI calculator
Equated monthly installment (reducing balance).
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Empirical formula calculator
Empirical formula from mole amounts or from mass percent composition.
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Energy conversion (percent efficiency)
E_out = η E_in with η as a percent.
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Energy converter
J, kJ, and kcal (thermochemical).
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Energy converter
J, eV, kcal, and other energy units.
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Enthalpy change calculator (ΔH from formation data)
Reaction enthalpy ΔH° from standard formation enthalpies: Σ ν ΔH_f°(products) − Σ ν ΔH_f°(reactants).
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Entropy change calculator (ΔS from S° data)
Reaction entropy ΔS° from standard molar entropies S° in J/(mol·K) for products and reactants.
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Enzyme activity (toy)
v = k[E][S] mass-action sketch.
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Equilibrium constant K_p and K_c calculator
Convert K_p ↔ K_c using Δn_gas and RT (gas-phase reactions).
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Equivalent weight calculator
Equivalent weight (g/eq) from molar mass and equivalents per mole.
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Error calculation
Absolute, relative, and percent error from measured and accepted values.
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Escape velocity
v_esc = √(2GM/r) from a spherical body.
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Evolutionary distance (p-distance)
Uncorrected DNA mismatch proportion.
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Exam cutoff check (toy)
Compare your toy score to a guessed cutoff.
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Exam time management planner
Split total time across questions with a review buffer.
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