Can I solve for different variables?

Yes! This calculator supports reverse solving. You can solve for: Energy, Charge, Voltage.

What units can I use?

This calculator supports multiple unit systems. Select your preferred units from the dropdown menus next to each input field.

Joules to Volts Calculator

Convert between joules, coulombs, and volts to understand capacitor energy or battery output.

Formula shown2 inputs definedFree, no sign-up

Quick Summary

Use this when you need:

Size capacitors when you know stored energy and charge
Convert battery pack specs between amp hours and watt hours
Explain how much voltage a given coulomb charge will produce

You’ll need:Energy, Charge

You’ll get:Voltage

How this is calculated

Formula:

voltage = energy / charge

In plain language:

The electrical relation V = J / C lets us compute the unknown when any two of voltage, energy (joules), or charge (coulombs or amp hours) are known.

The formula is always visible so you can verify the math and explain your numbers to anyone who asks.

What these terms mean

Energy

Energy used in the calculation.

Charge

Charge used in the calculation.

Voltage

Voltage used in the calculation.

When to use this calculator

Size capacitors when you know stored energy and charge
Convert battery pack specs between amp hours and watt hours
Explain how much voltage a given coulomb charge will produce

Last updated: November 18, 2025

Joules to volts explained

Electric potential (volts) tells you how much energy each coulomb of charge carries. Capacitor design, battery pack specs, and physics labs all use the fundamental relation $V = \tfrac{J}{C}$ . Our Joules to Volts Calculator lets you enter any two of energy, charge, or voltage—including amp-hours and watt-hours—to solve for the missing value.

How the conversion works

Start from the work definition of electric potential:

V = \frac{W}{q} = \frac{\text{joules}}{\text{coulombs}}

If you know voltage and charge, compute energy ( $J = V \times q$ ). If you know voltage and energy, solve for charge ( $q = \tfrac{J}{V}$ ). The calculator also converts Ah ↔ coulombs ( $1\,\text{Ah} = 3{,}600\,\text{C}$ ) and Wh ↔ joules ( $1\,\text{Wh} = 3{,}600\,\text{J}$ ) automatically.

Units and conversions

Quantity	Relation
Coulomb	$1\,\text{C} = 1\,\text{A} \cdot \text{s}$
Amp-hour	$1\,\text{Ah} = 3{,}600\,\text{C}$
Watt-hour	$1\,\text{Wh} = 3{,}600\,\text{J}$
Volt	$1\,\text{V} = 1\,\text{J}/\text{C}$

Worked examples

Capacitor energy
A 2 F capacitor charged to 12 V stores how much energy?

E = V \times q = 12 \times (C \cdot V) = 12^2 \times 1\,\text{F} / 2 = 144\,\text{J}

Result: 144 joules.

Battery pack voltage
A battery stores 90 Wh and has a 7.5 Ah rating. Compute nominal voltage.

\text{J} = 90 \times 3{,}600 = 324{,}000\\ \text{C} = 7.5 \times 3{,}600 = 27{,}000\\ V = \frac{324{,}000}{27{,}000} = 12\,\text{V}

Result: roughly a 12 V pack.

Tips and pitfalls

Keep energy and charge in consistent units (joules and coulombs) before dividing; the calculator converts amp-hours and watt-hours for you.
When working with capacitors, remember that $q = C \times V$ —combine it with $V = J/q$ to move between capacitance, energy, and voltage safely.
For batteries, rated amp-hours assume a specific discharge rate; actual voltage under load will sag even if the nominal $J/C$ math says 12 V.
Never exceed a capacitor’s voltage rating even if the energy you need seems small—the dielectric fails based on volts, not joules.

References and further reading

Frequently Asked Questions

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Version:: v1.0.0
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Last updated: November 18, 2025

Joules to volts explained

How the conversion works

Start from the work definition of electric potential:

V = \frac{W}{q} = \frac{\text{joules}}{\text{coulombs}}

Units and conversions

Quantity	Relation
Coulomb	$1\,\text{C} = 1\,\text{A} \cdot \text{s}$
Amp-hour	$1\,\text{Ah} = 3{,}600\,\text{C}$
Watt-hour	$1\,\text{Wh} = 3{,}600\,\text{J}$
Volt	$1\,\text{V} = 1\,\text{J}/\text{C}$

Worked examples

Capacitor energy
A 2 F capacitor charged to 12 V stores how much energy?

E = V \times q = 12 \times (C \cdot V) = 12^2 \times 1\,\text{F} / 2 = 144\,\text{J}

Result: 144 joules.

Battery pack voltage
A battery stores 90 Wh and has a 7.5 Ah rating. Compute nominal voltage.

\text{J} = 90 \times 3{,}600 = 324{,}000\\ \text{C} = 7.5 \times 3{,}600 = 27{,}000\\ V = \frac{324{,}000}{27{,}000} = 12\,\text{V}

Result: roughly a 12 V pack.

Tips and pitfalls

Keep energy and charge in consistent units (joules and coulombs) before dividing; the calculator converts amp-hours and watt-hours for you.
When working with capacitors, remember that $q = C \times V$ —combine it with $V = J/q$ to move between capacitance, energy, and voltage safely.
For batteries, rated amp-hours assume a specific discharge rate; actual voltage under load will sag even if the nominal $J/C$ math says 12 V.
Never exceed a capacitor’s voltage rating even if the energy you need seems small—the dielectric fails based on volts, not joules.

Quick Summary

Calculator Tool

How this is calculated

What these terms mean

Energy

Charge

Voltage

When to use this calculator

Joules to volts explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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Calculator info

Joules to volts explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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Nm to Joules Calculator

Activity coefficient

Acreage Calculator

Acres to Hectares Converter

Acres to Square Feet Converter

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