---
title: "Pharmacy Conversion Chart — Metric, Household, Apothecary"
description: "The complete US pharmacy conversion chart — metric, household, weight, apothecary, temperature — with must-memorize highlights and an unlimited conversion drill."
updated: 2026-08-03
canonical: https://ptcbready.com/pharmacy-tech-math/conversions
source-hash: ad5287978527f142
sources:
  - "NIST SP 811 — guide for the use of SI units (exact factors)": https://www.nist.gov/pml/special-publication-811
  - "US pharmacy dispensing convention (rounded values used in calculations on the PTCE)": https://ptcb.org/wp-content/uploads/2025/07/PTCE-Content-Outline.pdf
---

# Pharmacy Conversion Chart — Metric, Household, Apothecary

> The complete US pharmacy conversion chart — metric, household, weight, apothecary, temperature — with must-memorize highlights and an unlimited conversion drill.

## Metric — mass

| From | To | Must-memorize | Example |
| --- | --- | --- | --- |
| 1 kg | 1,000 g | YES | 0.5 kg = 500 g — shift the decimal 3 places right |
| 1 g | 1,000 mg | YES | 0.25 g = 250 mg — the classic trap: 0.025 g is 25 mg, not 250 |
| 1 mg | 1,000 mcg | YES | 0.125 mg = 125 mcg (levothyroxine strengths live here) |

## Metric — volume

| From | To | Must-memorize | Example |
| --- | --- | --- | --- |
| 1 L | 1,000 mL | YES | 2.5 L = 2,500 mL |
| 1 dL | 100 mL |  |  |

## Household

| From | To | Must-memorize | Example |
| --- | --- | --- | --- |
| 1 teaspoon (tsp) | 5 mL | YES | 2 tsp TID = 30 mL/day |
| 1 tablespoon (tbsp) | 15 mL | YES | 1 tbsp BID = 30 mL/day → a 300 mL bottle lasts 10 days |
| 1 fluid ounce (fl oz) | 30 mL (29.57 exact) | YES | 4 fl oz = 120 mL |
| 1 cup | 240 mL (8 fl oz) | YES |  |
| 1 pint | 480 mL convention (473 exact) | YES | Pharmacy stock bottles: 16 fl oz × 30 = 480 mL |
| 1 quart | 960 mL convention (946 exact) |  |  |
| 1 gallon | 3,840 mL convention (3,785 exact) |  |  |

## Body weight & avoirdupois

| From | To | Must-memorize | Example |
| --- | --- | --- | --- |
| 1 kg | 2.2 lb | YES | 154 lb ÷ 2.2 = 70 kg — divide by 2.2 going to kg (mg/kg dosing) |
| 1 oz | 28.35 g |  |  |

## Apothecary (legacy)

| From | To | Must-memorize | Example |
| --- | --- | --- | --- |
| 1 grain (gr) | 65 mg convention (64.8 exact) | YES | gr v = 5 × 65 = 325 mg (aspirin/acetaminophen) |
| gr ss | ½ grain ≈ 32.5 mg |  |  |

## Temperature

| From | To | Must-memorize | Example |
| --- | --- | --- | --- |
| °F → °C | (°F − 32) × 5⁄9 | YES | 77 °F = (77 − 32) × 5/9 = 25 °C — room temperature storage |
| °C → °F | °C × 9⁄5 + 32 | YES | 2–8 °C (refrigerated) = 36–46 °F |

## Roman numerals (sig usage)

| From | To | Must-memorize | Example |
| --- | --- | --- | --- |
| ss · i · v · x | ½ · 1 · 5 · 10 | YES | tabs iss = 1½ tablets |
| l · c · d · m | 50 · 100 · 500 · 1,000 |  |  |
| Subtraction rule | smaller before larger subtracts |  | iv = 4, ix = 9, xl = 40 |


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Cite as: PTCB Ready, updated 2026-08-03. Interactive version: https://ptcbready.com/pharmacy-tech-math/conversions