Local Anesthetic Calculator

Find the maximum recommended dose and volume of a local anesthetic from patient weight, the agent's mg/kg limit, and the solution's percent concentration.

Quick Facts

Core formula
Max dose (mg) = weight (kg) x mg/kg limit
Capped at the agent's absolute adult ceiling, then divided by concentration (mg/mL) for max volume.
Percent to mg/mL
% x 10 = mg/mL
A 1% solution contains 10 mg of drug per mL; a 2% solution contains 20 mg/mL.

Your Results

Calculated
Maximum safe dose
-
Weight x mg/kg, capped at the absolute max
Maximum safe volume
-
Max dose at this concentration
Planned dose
-
From your planned volume
Percent of maximum
-
Planned dose / maximum dose

Ready

Enter patient weight, agent, formulation, and concentration, then calculate the maximum safe dose.

About the local anesthetic max dose calculator

This calculator applies the standard maximum recommended dose (MRD) method used in anesthesiology, dentistry, and emergency medicine to keep injected local anesthetic below the threshold associated with systemic toxicity. Every commonly used agent has a published milligrams-per-kilogram limit and, in most cases, an absolute adult ceiling that applies even to larger patients. The tool multiplies your entered weight by the agent's mg/kg limit, caps the result at that ceiling, and converts the answer into a maximum injectable volume based on the concentration of the solution you selected.

The formula, step by step

  • Weight-based ceiling: maximum dose (mg) = patient weight (kg) x the agent's mg/kg limit.
  • Absolute cap: the weight-based figure is capped at the drug's published adult maximum, since very heavy patients do not get an unlimited dose.
  • Concentration conversion: a percent concentration converts to mg/mL by multiplying by 10 (a 1% solution is 10 mg/mL, a 2% solution is 20 mg/mL).
  • Maximum volume: maximum dose (mg) divided by concentration (mg/mL) gives the maximum safe volume in mL.
  • Planned dose check: your planned injection volume multiplied by the same mg/mL figure gives the dose you intend to deliver, which the tool compares against the maximum as a percentage.

Why epinephrine changes the limit

Epinephrine constricts the blood vessels around the injection site, which slows how quickly the anesthetic is absorbed into the bloodstream and lowers peak plasma concentration for a given dose. Because systemic toxicity tracks peak plasma level, published references allow a higher mg/kg limit and a higher absolute maximum for epinephrine-containing formulations than for the same drug given plain.

When to consult a professional

This calculator performs the standard arithmetic used to estimate a maximum safe dose; it is not a substitute for clinical judgment. Actual practice should account for the patient's age, hepatic and renal function, cardiac status, site of injection, and any other medications, and any dose near or above the calculated maximum should be reviewed with a licensed prescriber or anesthesia provider before administration.

Frequently Asked Questions

How is the maximum local anesthetic dose calculated?
The maximum recommended dose (MRD) is patient weight in kilograms multiplied by the agent's milligrams-per-kilogram limit, capped at the drug's absolute adult ceiling regardless of weight. That dose in milligrams is then divided by the solution's concentration in mg/mL (percent concentration times 10) to get the maximum safe volume in mL.
Why does adding epinephrine raise the maximum dose?
Epinephrine constricts blood vessels at the injection site, which slows systemic absorption of the anesthetic and lowers peak blood levels for a given dose. Standard references therefore list a higher mg/kg ceiling and a higher absolute maximum for epinephrine-containing formulations than for the plain (epinephrine-free) version of the same drug.
How do I convert a percent concentration to mg/mL?
A percent concentration is grams per 100 mL, so multiply the percent by 10 to get milligrams per mL. A 1% solution is 10 mg/mL, a 2% solution is 20 mg/mL, and a 0.25% solution is 2.5 mg/mL. Multiplying that mg/mL figure by the injected volume gives the delivered dose in milligrams.

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