Millifarad to Microfarad: Reading Capacitor Values in Electronics

A power supply filter stage was redesigned with a bulk capacitor sourced from a distributor. The BOM called for a 10 µF electrolytic — a standard filter cap. The engineer browsed the catalog and selected 10 mF, reading the "m" as millifarads without registering the 1,000× difference. At power-on, the inrush current required to charge a 10 mF capacitor through the 5 Ω source impedance peaked at nearly 40 A — well above the 2 A input fuse rating. The fuse blew on first power-on. Three boards were damaged before the BOM error was found.

10 µF and 10 mF look almost identical in a catalog search. They are not. One is 1,000 times larger than the other.

To convert millifarads (mF) to microfarads (µF), multiply by 1,000. To convert microfarads (µF) back to millifarads (mF), divide by 1,000. Use the mF to µF converter to verify any capacitor value before BOM submission.

Calculate Instantly

When cross-referencing datasheets, BOM specs, and catalog values, convert between mF and µF without guessing.

The Capacitance Prefix Chain

Capacitance values in electronics span from picofarads (pF) in RF circuits to millifarads (mF) in supercapacitor energy storage. The most common design range is microfarads (µF) and nanofarads (nF). Millifarads (mF) appear mainly in:

• Supercapacitors (also called ultracapacitors or EDLC cells)
• Large electrolytic bulk storage capacitors
• Energy harvesting buffer capacitors

graph TD
    MF[Millifarad<br>10⁻³ F] -->|"× 1,000"| UF[Microfarad<br>10⁻⁶ F]
    UF -->|"× 1,000"| NF[Nanofarad<br>10⁻⁹ F]
    NF -->|"× 1,000"| PF[Picofarad<br>10⁻¹²  F]
    style MF fill:#4c1d95,color:#fff
    style UF fill:#7c3aed,color:#fff
    style NF fill:#d946ef,color:#fff
    style PF fill:#22d3ee,color:#111

1 mF = 1,000 µF = 1,000,000 nF = 1,000,000,000 pF

For the underlying prefix math, see understanding SI prefixes and milli to micro conversion.

Common Capacitor Applications by Scale

For current draw calculations related to capacitor charge/discharge, see milliampere vs microampere. For timing capacitors in RC circuits, see milliseconds vs microseconds — the RC time constant τ = R × C directly links capacitance to timing.

The mF to µF Conversion Table

For the reverse, use the µF to mF converter.

Reading Capacitor Markings

Electrolytic capacitors print their value directly (e.g., "100µF 25V"). Ceramic and film capacitors often use a 3-digit code in pF:

• 104 = 10 × 10⁴ pF = 100,000 pF = 100 nF = 0.1 µF
• 225 = 22 × 10⁵ pF = 2,200,000 pF = 2.2 µF
• 473 = 47 × 10³ pF = 47,000 pF = 47 nF

None of these markings use the mF scale. If a catalog listing shows mF for a standard ceramic or film cap, treat it as a likely unit error — verify against the datasheet. For mV/µV signal applications with capacitors, see millivolts to microvolts.

Frequently Asked Questions

How many microfarads are in a millifarad? Exactly 1,000 µF = 1 mF. This is an SI-defined exact relationship. Use the mF to µF converter for specific values.

Is millifarad a common capacitor unit? Not in standard PCB design. Most designers work in µF (microfarads) and nF (nanofarads). Millifarads (mF) appear primarily in supercapacitors and large bulk energy storage. If a BOM or catalog spec shows mF for what should be a standard bypass or filter capacitor, verify it — the value may be a misprint or unit confusion.

What is the difference between mF and µF? A millifarad (mF) is 10⁻³ F — one thousandth of a farad. A microfarad (µF) is 10⁻⁶ F — one millionth of a farad. 1 mF = 1,000 µF. In a circuit, this is the difference between a 10 µF electrolytic filter cap and a 10 mF supercapacitor — two completely different components with completely different behaviors and footprints.

How does capacitor value affect RC timing? RC time constant τ = R × C. If R = 1,000 Ω and C = 10 µF = 0.00001 F, τ = 10 ms. If the capacitor is actually 10 mF = 0.01 F, τ = 10 s — a 1,000× timing error that makes a debounce circuit or oscillator behave completely differently. See milliseconds vs microseconds for timing-scale implications.

Why do capacitor datasheets sometimes list values in different units? There is no universal convention. Some manufacturers list in µF, others in nF, others in pF — and occasionally in mF for large values. Always check the unit column, not just the number. A 100 µF value and a 100 nF value are both "100" in different columns — and 1,000× different in practice.

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Next: Capacitor values interact directly with power budgets — see Milliwatts to Microwatts: Power Budgeting for Wireless and Energy Harvesting.

Sources

• NIST Special Publication 811 — Guide for the Use of the International System of Units
• BIPM: SI Prefixes
• IEC 60062: Marking codes for resistors and capacitors
• Murata: Capacitor Selection Guide — unit and marking conventions
• IEEE 754 Standard for Floating-Point Arithmetic