The Complete SI Prefix Conversion Chart: Pico to Giga

The International System of Units (SI) uses a single mechanism to express any quantity at any scale: a prefix multiplied by a base unit. One prefix, one rule, infinite range. A kilogram and a microgram are the same unit — gram — shifted by nine orders of magnitude using two prefixes. A nanosecond and a megasecond are the same unit — second — shifted by fifteen.

This is the complete reference. Every major SI prefix, its exact multiplier, its symbol, and how it converts to the prefixes beside it. Bookmark it. The rule that prevents 1,000× errors is at the end.

The Complete SI Prefix Chart

All 20+ SI prefixes are defined by BIPM in the official SI Brochure. The 12 above cover 99% of engineering and scientific use.

The One Rule Behind All of It

The SI prefix system is built on powers of ten. Converting between any two prefixes means finding the difference in their exponents and applying it as a power of 10.

Between adjacent major prefixes (giga ↔ mega ↔ kilo ↔ base ↔ milli ↔ micro ↔ nano ↔ pico): each step is exactly ×1,000 (10³).

graph LR
    G[Giga<br>10⁹] -->|"÷ 1,000"| M[Mega<br>10⁶]
    M -->|"÷ 1,000"| K[Kilo<br>10³]
    K -->|"÷ 1,000"| B[Base<br>10⁰]
    B -->|"÷ 1,000"| Mi[Milli<br>10⁻³]
    Mi -->|"÷ 1,000"| Mc[Micro<br>10⁻⁶]
    Mc -->|"÷ 1,000"| N[Nano<br>10⁻⁹]
    N -->|"÷ 1,000"| P[Pico<br>10⁻¹²]
    style G fill:#1e1b4b,color:#fff
    style M fill:#312e81,color:#fff
    style K fill:#4c1d95,color:#fff
    style B fill:#6d28d9,color:#fff
    style Mi fill:#7c3aed,color:#fff
    style Mc fill:#a855f7,color:#fff
    style N fill:#c084fc,color:#111
    style P fill:#e9d5ff,color:#111

Count the steps between any two prefixes. Multiply by 1,000 per step going down (toward smaller). Divide by 1,000 per step going up (toward larger).

Examples:

• Kilo → milli: 2 steps down → ×1,000,000 (1 km = 1,000,000 mm)
• Micro → nano: 1 step down → ×1,000 (1 µs = 1,000 ns)
• Nano → kilo: 4 steps up → ÷1,000,000,000,000 (1 nm = 0.000000000001 km)
• Giga → micro: 5 steps down → ×10¹⁵ (1 GHz = 1,000,000,000,000,000 µHz)

Quick-Convert Calculator

For specific unit pairs, use the dedicated converters: mm to µm · mA to µA · mV to µV · mg to µg · ms to µs · mL to µL · mF to µF · mW to µW · browse all 40 converters.

---

Prefix-to-Prefix Conversion Tables

The Four Most Common Engineering Steps

These four adjacent-prefix conversions cover the vast majority of errors seen in practice.

Kilo ↔ Base ↔ Milli (3 steps, ×1,000 each)

Milli ↔ Micro (1 step, ×1,000)

The most common prefix confusion in electronics, medicine, chemistry, and computing. Every post in this series covers a domain-specific application.

Micro ↔ Nano (1 step, ×1,000)

Nano ↔ Pico (1 step, ×1,000)

---

The Same Rule Across Every Physical Quantity

The prefix is independent of the base unit. The multiplication factor is the same whether you are working in length, current, mass, time, voltage, or energy. This is the power of the SI system — one mental model covers all quantities.

Full Cross-Prefix Reference: Length

Full Cross-Prefix Reference: Time

Full Cross-Prefix Reference: Electric Current

---

The Direction Rule: Never Guess

When converting between prefixes, the direction is the most common error point. Use this test every time:

Moving to a smaller unit → number gets larger. Moving to a larger unit → number gets smaller.

If your converted number shrank while you moved to a smaller unit, you divided when you needed to multiply. The error is always in the direction, never in the factor.

---

Frequently Asked Questions

What is the difference between metric prefixes and SI prefixes? SI prefixes are the internationally standardized set defined by the BIPM (Bureau International des Poids et Mesures). "Metric prefixes" is informal shorthand for the same set. All SI prefixes are metric; all standard metric prefixes are SI.

Which prefix is 1,000 times smaller than milli? Micro (µ). 1 milli = 1,000 micro. The next step below micro is nano — 1,000 times smaller than micro, 1,000,000 times smaller than milli.

How many nanometers are in a millimeter? 1 mm = 1,000 µm = 1,000,000 nm. Two steps on the prefix ladder (milli → micro → nano), each ×1,000, gives ×1,000,000 total.

What is the difference between µ (micro) and m (milli) in a unit symbol? Capitalization and the symbol itself both matter. m = milli (10⁻³). µ = micro (10⁻⁶). M = mega (10⁶). These are distinct — mA (milliampere) and µA (microampere) are 1,000× different currents. In plain text where µ is unavailable, "u" is the accepted ASCII substitute (uA, um, us).

How do I remember the prefix order from large to small? A common mnemonic for the major prefixes from large to small: "Good Mechanics Know How Dirty Centimeters Make Measuring Nasty, Particularly Frustrating" — Giga, Mega, Kilo, Hecto, Deca, Centi, Milli, Micro, Nano, Pico, Femto. The ones that matter most in engineering: Giga–Kilo–Base–Milli–Micro–Nano–Pico, each 1,000× from its neighbor.

Where can I convert specific unit pairs? Use the dedicated converters: mm to µm, mA to µA, mV to µV, mg to µg, ms to µs, mL to µL, mF to µF, mW to µW, or browse all 40 converters.

---

Next: See how getting these prefixes wrong has shut down factories, recalled products, and cost lives — How Wrong Units Cost Engineers Millions: Real-World Conversion Disasters.

Sources

• BIPM: SI Brochure — The International System of Units (9th edition)
• NIST Special Publication 811 — Guide for the Use of the International System of Units
• NIST: Metric (SI) Prefixes — official table
• ISO 80000-1: Quantities and Units — General