Pharmacology
Serial Dose Calculator
Turn a human tablet into a dose small enough for a mouse or a rat: dissolve it, dilute it tube by tube, and draw the exact volume into the syringe.
Dose in the syringe
0.009mg
9 µg · 0% vs the 0.009 mg target — within ±5%
Stock C₀
2.5
mg/mL
Syringe C
0.09
mg/mL
Dilution
1:27.778×
2 tubes
Dose parameters
Every value updates the chain as you type.
Worked examples
The drug in the whole tablet or solid you dissolve.
Volume of diluent for the stock (Tube 0).
= 9 µg
The volume you will inject.
Moved from each tube to the next when the plan is made. Empty or 0 uses 1 mL.
Bench plan
Planned in 1:10 steps with the last step making up the remainder. Edit any volume to take over.
Stock solution
Tube 0Dissolve 25 mg in 10 mL of diluent.
C₀ = 2.5 mg/mL
Tube 1
1:10×C = 0.25 mg/mLtotal 10 mL
Tube 2
1:2.778×C = 0.09 mg/mLtotal 2.778 mL
Into the syringe
0.1 mLDraw exactly 0.1 mL from Tube 2 into a sterile precision syringe.
Delivered
0.009 mg
9 µg
Target
0.009 mg
9 µg
Match
0%
Within ±5%
C₀ = 25 mg ÷ 10 mL = 2.5 mg/mL
C(syringe) = 0.009 mg ÷ 0.1 mL = 0.09 mg/mL
Dilution needed = 2.5 ÷ 0.09 = 1:27.778×
Tube 1: 2.5 × 1 ÷ (1 + 9) = 0.25 mg/mL
Tube 2: 0.25 × 1 ÷ (1 + 1.778) = 0.09 mg/mL
Dose = 0.09 mg/mL × 0.1 mL = 0.009 mg (9 µg)
The rules. Dilution law C₁V₁ = C₂V₂: stock concentration × volume taken = new concentration × total volume. Step dilution = total volume ÷ volume taken, so 1 mL into 9 mL of diluent is 1:10. Dose = final concentration × syringe volume; × 1000 turns mg into µg.
How the plan is made. While more than a 1:10 dilution remains, a tube takes the default transfer and makes it up ten-fold; the last tube makes up only what is left. Volumes are rounded to 4 decimal places, which is why a planned chain can land a hair off the target (35 µg shows as 34.999 µg). The plan stops at six tubes.
Keep learning
References
- Stockton SJ. Stoklosa and Ansel's Pharmaceutical Calculations. 16th ed. Philadelphia: Wolters Kluwer; 2021.
Common questions
Because a 9 µg dose is far below what a lab balance can weigh accurately, and a fraction of a tablet is not evenly loaded with drug. Dissolving the whole tablet and diluting it in measured volumes turns an impossible weighing into a few ordinary pipetting steps.
Ten-fold steps keep every transfer a comfortable, accurate volume (1 mL into 9 mL) and make each tube's concentration easy to check by eye. The final tube makes up only the remaining factor, so the syringe volume carries the exact dose.
Yes. Edit the volume taken or the diluent in any tube and the whole chain — every later tube, the syringe dose and the ±5% check — recalculates from your numbers. "Back to auto-plan" discards your edits.
It compares the dose the syringe would actually deliver with the target you entered. Outside ±5%, the chain you have does not give the dose you asked for, usually because a tube's volumes were edited or the plan ran out of tubes.
From the animal's mg/kg dose × its body weight, or a published animal dose. This calculator starts from that mg figure; it does not scale a human dose to an animal.
Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy