Example data table
| Scenario | Model | Inputs | Raw energy (J) | Net energy (J) | Approx kWh (raw) |
|---|---|---|---|---|---|
| Bike sprint | Kinetic | m=80 kg, v=10 m/s | 4,000 | 3,420 | 0.00111 |
| Lift a crate | Potential | m=30 kg, h=2 m | 588 | 503 | 0.000163 |
| Heat water | Thermal | m=1 kg, c=4184, ΔT=20 °C | 83,680 | 71,546 | 0.0232 |
| Small appliance | Electrical | P=1200 W, t=10 min | 720,000 | 615,600 | 0.200 |
| Compressed spring | Spring | k=500 N/m, x=0.10 m | 2.5 | 2.14 | 0.000000694 |
Net values assume 90% efficiency and 5% losses for illustration. Use the calculator for exact conversions and your own assumptions.
Values are rounded for readability. Use the calculator for exact conversions.
Formulas used
- Kinetic:
E = 0.5 × m × v² - Gravitational potential:
E = m × g × h - Thermal:
E = m × c × ΔT - Electrical:
E = P × torE = V × I × t - Spring:
E = 0.5 × k × x² - Fuel / chemical:
E = m × energy_density
Efficiency and losses
Net energy is calculated as E_net = E_raw × (efficiency/100) × (1 − losses/100). Use this to estimate delivered or usable energy.
How to use this calculator
- Select the energy model that matches your scenario.
- Enter inputs and choose the correct units.
- Set efficiency and losses to reflect real conditions.
- Click Calculate to see raw and net energy.
- Use the conversion table for kWh, kcal, or BTU.
- Download CSV or PDF to save your results.
Energy facts for fast estimates
This page lets you compute energy from work, motion, heat, electricity, and fuels in one place. Enter any known inputs, choose units, and apply efficiency or losses. Results are shown in Joules, kJ, MJ, Wh, and kWh for easy comparison. It also provides net totals for quick comparisons.
1) Unit conversions you will use most
Use Joules for physics and kWh for electricity bills. 1 kWh = 3.6 MJ. 1 Wh = 3600 J. 1 calorie (food) = 4184 J. 1 BTU ≈ 1055 J. This calculator converts common inputs into Joules before computing totals.
2) Work and potential energy data
For lifting, E = m·g·h with g = 9.80665 m/s². Lifting a 30 kg crate by 2 m needs about 588 J. A 75 kg person climbing 3 m uses about 2206 J of mechanical gain, before efficiency losses are considered.
3) Kinetic and impact energy data
Kinetic energy is E = ½·m·v². A 0.15 kg ball at 25 m/s carries 46.9 J. A 1.2 tonne car at 13.9 m/s (50 km/h) has about 116 kJ, showing why speed dominates: doubling velocity makes energy 4×.
4) Thermal heating data
Heating uses E = m·c·ΔT. Water has c ≈ 4184 J/(kg·°C). Heating 1 kg of water by 20 °C needs 83,680 J (23.2 Wh). Melting ice needs latent heat: 334 kJ/kg at 0 °C.
5) Electrical usage data
Electrical energy is E = P·t. A 1200 W appliance running 10 minutes uses 0.200 kWh. A 60 W lamp for 5 hours uses 0.300 kWh. For motors, add efficiency: input energy = output/η.
6) Fuel and chemical energy data
For fuels, E = m·energy_density or V·energy_density. Typical lower heating values: gasoline ≈ 34 MJ/L, diesel ≈ 36 MJ/L, propane ≈ 25 MJ/L. A 1 L gasoline equivalent is close to 9.4 kWh of chemical energy.
7) Efficiency, losses, and reality checks
Human mechanical efficiency is often 20–25%. Electric kettles can exceed 85–90% into water, while older engines may deliver 20–35% to the wheels. Use the “Efficiency” and “Loss” fields to estimate net energy and compare scenarios fairly.
FAQs
What does “net energy” mean here?
Net energy is the usable energy after losses are applied. The calculator starts with gross energy from the selected method, then multiplies by efficiency and subtracts any explicit loss value so you can compare realistic outcomes.
Which unit should I report in?
Use Joules or kJ for scientific work and engineering notes. Use kWh for electricity usage and cost estimates. The page shows both, so pick the unit that matches your audience and billing or specification sheets.
How do I handle efficiency for motors or heaters?
If you know output energy, divide by efficiency to estimate required input. If you know input energy, multiply by efficiency to estimate output. In this calculator, enter your measured energy and then set efficiency to get the net result.
Can I combine different energy types?
Yes. Compute one scenario, then adjust inputs and compare totals side by side. Because everything is converted to Joules internally, work, kinetic, thermal, electrical, and fuel estimates can be compared directly in a consistent unit system.
Why does speed change kinetic energy so much?
Kinetic energy depends on velocity squared. When speed doubles, energy becomes four times larger. That relationship makes small speed increases produce large energy increases, which is important for impact estimates and braking distance discussions.
What inputs give the most reliable results?
Use measured values when possible: mass from a scale, distance from a tape, time from a stopwatch, and electrical power from a meter. Then apply realistic efficiency ranges. Overly optimistic efficiencies can make the net energy look misleading.