Veterinary Dilution Calculator (C1V1 = C2V2)
C1V1 = C2V2, with safer bag, reverse-check and serial-dilution workflows. Enter what is on the vial, what you need and the final volume. Works in %, mg/mL, mcg/mL, g/L, mEq/mL, IU/mL and ratio strengths.
What you have and what you want
Common dilutions vet presets, optional starting point
Measurement safety setting
Draw up this much drug
For use by veterinary professionals. This tool is deterministic arithmetic applied to the numbers you type. It does not know your drug, your patient or your product label. Check that the stock concentration you entered matches the vial in your hand, that the drug is compatible with the diluent, and that the diluted product is used within its stability window. Dilutions prepared outside a pharmacy are for immediate use unless your practice has validated otherwise. Label every syringe and container with drug, concentration, diluent, date, time and initials. Two-person independent checks are recommended for any dilution of a controlled or high-risk drug.
Method: C1V1 = C2V2, where C1 is the stock concentration, V1 the volume of stock to draw up, C2 the concentration you want and V2 the final total volume. Select % w/v only when the label explicitly states weight per volume; then 1% w/v = 1 g per 100 mL = 10 mg/mL. Ratio strengths are treated as grams per volume, so 1:1000 = 1 g in 1000 mL = 1 mg/mL.
How to dilute a drug: the C1V1 = C2V2 method
Quick answer. To dilute anything, multiply the concentration you want by the final volume you want, then divide by the concentration you have. That gives you the volume of stock drug to draw up. Everything else in the container is diluent. In symbols, V1 = (C2 × V2) ÷ C1, and the diluent volume is V2 − V1. Example: to make 10 mL of 0.1 mg/mL adrenaline from a 1 mg/mL (1:1000) vial, V1 = (0.1 × 10) ÷ 1 = 1 mL of adrenaline plus 9 mL of saline.
What each letter means
| Symbol | Name | What it is in real life |
|---|---|---|
| C1 | Initial concentration | The strength printed on the vial you are holding. The stock. |
| V1 | Initial volume | The number you are usually solving for. How many mL of the neat drug to draw up. |
| C2 | Final concentration | The strength you want to end up with. |
| V2 | Final volume | The total volume in the syringe or container when you have finished, including the drug. |
The equation works because the amount of drug does not change when you dilute it. You are only spreading the same amount of drug through more liquid. C1V1 is the amount of drug you draw up; C2V2 is that same amount sitting in a bigger volume.
The one rule that catches people out: C1 and C2 must be in the same unit. If the vial is a percentage and your target is mg/mL, convert one of them first. This calculator converts for you and shows the mg/mL equivalent under every box, because the percent-to-mg/mL slip is the most common dilution error in practice.
Two ways to physically make it
In a syringe. Draw up V1 mL of drug, then draw diluent up to the V2 mark. The drug volume is part of the final volume, not on top of it.
In a bag or bottle. If you want the bag to stay at its labelled volume, remove V1 mL of fluid from the bag first, then add V1 mL of drug. If you simply inject the drug on top without removing anything, the final volume is bag + drug, so the final concentration is slightly lower than C1V1 = C2V2 predicts. This tool handles both, and uses the correct formula V1 = (C2 × Vbag) ÷ (C1 − C2) for the add-on-top method.
The one assumption the equation makes
C1V1 = C2V2 assumes the diluent contains none of the substance you are diluting. That is true almost always, and false in two places that matter. If you dilute concentrated saline with 0.9% sodium chloride, the diluent is already 9 mg/mL of the very thing you are diluting, so the finished solution comes out stronger than the equation predicts. Making 100 mL of 7.2% saline from a 23.4% concentrate needs 30.8 mL if you use sterile water, but only 28.0 mL if you use 0.9% saline, and using the water figure with saline gives you 7.8%. The same applies to diluting 50% dextrose with 5% dextrose. Dilute with sterile water in those cases, or let the calculator correct it: it flags this and prints the adjusted volume.
Percent, mg/mL and ratio strengths
Use the % w/v unit only when the product label explicitly states weight per volume. In that system, 1% w/v is 1 gram in 100 mL, or 10 mg/mL, so multiply the percentage by 10 to convert to mg/mL. Do not apply that shortcut to % w/w or % v/v. Ratio strengths mean grams per volume: 1:1000 is 1 gram in 1000 mL, which is 1 mg/mL.
| Label says | Same as mg/mL | Same as mcg/mL | Typical example |
|---|---|---|---|
| 0.05% | 0.5 mg/mL | 500 mcg/mL | Chlorhexidine wound lavage |
| 0.25% | 2.5 mg/mL | 2,500 mcg/mL | Bupivacaine, diluted |
| 0.5% | 5 mg/mL | 5,000 mcg/mL | Bupivacaine, neat |
| 1% | 10 mg/mL | 10,000 mcg/mL | Lidocaine, diluted; propofol |
| 2% | 20 mg/mL | 20,000 mcg/mL | Lidocaine, neat |
| 4% | 40 mg/mL | 40,000 mcg/mL | Chlorhexidine surgical scrub |
| 7.2% | 72 mg/mL | 72,000 mcg/mL | Hypertonic saline |
| 8.4% | 84 mg/mL | 84,000 mcg/mL | Sodium bicarbonate |
| 10% | 100 mg/mL | 100,000 mcg/mL | Calcium gluconate, povidone-iodine |
| 23.4% | 234 mg/mL | 234,000 mcg/mL | Concentrated saline |
| 50% | 500 mg/mL | 500,000 mcg/mL | Dextrose |
| 1:100 | 10 mg/mL | 10,000 mcg/mL | 1% adrenaline, topical or inhalational only, never injected |
| 1:1000 | 1 mg/mL | 1,000 mcg/mL | Standard adrenaline ampoule |
| 1:10,000 | 0.1 mg/mL | 100 mcg/mL | Adrenaline for CPR dosing |
| 1:100,000 | 0.01 mg/mL | 10 mcg/mL | Adrenaline in local anaesthetic |
Common veterinary dilutions
These are arithmetic starting points, not mixing instructions. The table assumes a compatible, solute-free diluent unless the row says otherwise; open the live preset to choose the exact diluent, route and concentration basis, then verify the product label and your clinic protocol.
| Dilution | Have | Want | Makes | Draw up | Carrier volume | Why / key assumption |
|---|---|---|---|---|---|---|
| Adrenaline 1:1000 to 1:10,000 | 1:1000 | 1:10,000 | 10 mL | 1 mL | 9 mL | Low-dose IV adrenaline in CPR and accurate dosing in small patients |
| Atropine 0.6 mg/mL to 0.06 mg/mL | 0.6 mg/mL | 0.06 mg/mL | 10 mL | 1 mL | 9 mL | Neonates, small exotics and birds |
| Sodium bicarbonate 8.4% to 4.2% | 8.4 % (w/v) | 4.2 % (w/v) | 20 mL | 10 mL | 10 mL | Neonates and small patients, where undiluted 8.4% is too hyperosmolar |
| Dextrose 50% to 12.5% | 50 % (w/v) | 12.5 % (w/v) | 20 mL | 5 mL | 15 mL | Hypoglycaemia bolus, diluted 1 in 4 |
| Calcium gluconate 10% to 5% | 10 % (w/v) | 5 % (w/v) | 20 mL | 10 mL | 10 mL | Concentrations are calcium gluconate salt, not elemental calcium |
| Hypertonic saline 23.4% to 7.2% | 23.4 % (w/v) | 7.2 % (w/v) | 100 mL | 30.77 mL | 69.23 mL | Solute-free compatible diluent only; saline requires background correction |
| Naloxone 0.4 mg/mL to 0.04 mg/mL | 0.4 mg/mL | 0.04 mg/mL | 10 mL | 1 mL | 9 mL | Titrated opioid reversal after ventilation and resuscitation are established |
| Ketamine 100 mg/mL to 10 mg/mL | 100 mg/mL | 10 mg/mL | 10 mL | 1 mL | 9 mL | Small doses, top-ups and syringe driver loading |
| Buprenorphine 0.3 mg/mL to 0.03 mg/mL | 0.3 mg/mL | 0.03 mg/mL | 10 mL | 1 mL | 9 mL | Cats and small dogs |
| Methadone 10 mg/mL to 1 mg/mL | 10 mg/mL | 1 mg/mL | 10 mL | 1 mL | 9 mL | Accurate dosing in cats and small dogs |
| Butorphanol 10 mg/mL to 1 mg/mL | 10 mg/mL | 1 mg/mL | 10 mL | 1 mL | 9 mL | Cats, small dogs and exotics |
| Dexmedetomidine 0.5 mg/mL to 0.05 mg/mL | 0.5 mg/mL | 0.05 mg/mL | 10 mL | 1 mL | 9 mL | Microdoses and sedation top-ups |
| Medetomidine 1 mg/mL to 0.1 mg/mL | 1 mg/mL | 0.1 mg/mL | 10 mL | 1 mL | 9 mL | Microdoses and sedation top-ups |
| Fentanyl 50 mcg/mL to 5 mcg/mL | 50 mcg/mL | 5 mcg/mL | 10 mL | 1 mL | 9 mL | Small patients and fine titration |
| Midazolam 5 mg/mL to 1 mg/mL | 5 mg/mL | 1 mg/mL | 10 mL | 2 mL | 8 mL | Co-induction and seizure dosing in small patients |
| Acepromazine 2 mg/mL to 0.2 mg/mL | 2 mg/mL | 0.2 mg/mL | 10 mL | 1 mL | 9 mL | Low-dose titration, which is how acepromazine should be used |
| Glycopyrrolate 0.2 mg/mL to 0.02 mg/mL | 0.2 mg/mL | 0.02 mg/mL | 10 mL | 1 mL | 9 mL | Exotics and small patients when the exact formulation is suitable |
| Regular (soluble) insulin U-100 to U-10 | 100 IU/mL | 10 IU/mL | 10 mL | 1 mL | 9 mL | Small-patient dosing only when the exact product label permits dilution |
| Lidocaine 2% to 1% | 2 % (w/v) | 1 % (w/v) | 10 mL | 5 mL | 5 mL | Larger-volume local blocks without exceeding the toxic dose |
| Lidocaine 2% to 0.5% | 2 % (w/v) | 0.5 % (w/v) | 20 mL | 5 mL | 15 mL | Splash blocks, line blocks in cats and volume-limited blocks |
| Bupivacaine 0.5% to 0.25% | 0.5 % (w/v) | 0.25 % (w/v) | 10 mL | 5 mL | 5 mL | Larger-volume infiltration and cats |
| Potassium chloride into a 1 L bag at 20 mEq/L | 2 mEq/mL | 20 mEq/L | 1,000 mL | 10 mL | 990 mL | Confirm actual bag volume; Hartmann's requires its potassium-background correction |
| Oxytocin 10 IU/mL to 1 IU/mL | 10 IU/mL | 1 IU/mL | 10 mL | 1 mL | 9 mL | Small-patient uterine inertia dosing |
| Heparinised saline 1000 IU/mL to 10 IU/mL | 1,000 IU/mL | 10 IU/mL | 100 mL | 1 mL | 99 mL | Catheter flush solution |
| Chlorhexidine 2% aqueous to 0.05% | 2 % (w/v) | 0.05 % (w/v) | 500 mL | 12.5 mL | 487.5 mL | Open wound lavage |
| Povidone-iodine 10% to 1% | 10 % (w/v) | 1 % (w/v) | 500 mL | 50 mL | 450 mL | Open wound lavage |
| Iohexol 350 to 240 mg iodine/mL | 350 mg/mL | 240 mg/mL | 50 mL | 34.29 mL | 15.71 mL | Gastrointestinal and cystographic contrast studies |
When the volume is too small to measure
If the maths tells you to draw up 0.02 mL, you cannot do it accurately. A 1 mL syringe is graduated in 0.01 mL, and the dead space in the hub and needle is often larger than the dose itself. Below roughly 0.05 mL you are guessing, and in a 500 g kitten or a 30 g bird that guess is the whole safety margin.
The fix is a serial dilution. Dilute the stock by a round factor first, then draw a sensible volume from that intermediate solution. To dilute 1 in 10, take 1 mL of stock and add 9 mL of diluent. Every step multiplies your measurable volume by 10. The calculator does this automatically and prints both steps whenever the required volume falls below the measurable threshold.
Things that should not be diluted
Not everything survives dilution. Some products are emulsions or suspensions, some depend on pH or precipitation for their action, and some carry a preservative that stops working once it is diluted out.
- Propofol. An oil-in-water emulsion. Diluting it destabilises the emulsion, and most formulations have little or no preservative, so a diluted syringe is a bacterial growth medium.
- Insulin without checking the exact product and route. Glargine labels say not to dilute or mix, and detemir, PZI, lente and NPH are not interchangeable with regular soluble insulin. Some subcutaneous regular-insulin dilutions require a proprietary diluent; separately, some regular-insulin labels allow a defined IV concentration range in 0.9% sodium chloride. Follow the exact product label and keep SC dilution distinct from an IV CRI workflow.
- Diazepam. Precipitates in aqueous diluents and adsorbs to PVC. Use midazolam if you need a water-soluble benzodiazepine.
- Liposomal bupivacaine (Nocita). Species and indication matter: the dog label permits up to a 1:1 dilution with 0.9% saline or Hartmann's, while the labelled cat nerve block should not be diluted. Hypotonic solutions may disrupt liposomal particles. Never mix it with other local anaesthetics.
- Zenalpha (medetomidine with vatinoxan). Labelled not to be diluted or mixed, and it is half the strength of Domitor.
- Depot and long-acting suspensions, and transdermal products such as Zorbium buprenorphine, which is 20 mg/mL and never injected.
Mistakes worth avoiding
- Mixing units. Entering 2 for a 2% vial and 5 for a 5 mg/mL target gives a wrong answer that looks reasonable. Convert first, or let the tool do it.
- Adding the diluent to the drug volume instead of up to it. Drawing 1 mL of drug and then adding 10 mL of saline makes 11 mL, not 10 mL. The final concentration is 9% lower than you intended. That matters for a controlled drug infusion; it matters less for a lavage.
- Injecting into a bag without removing anything. Adding 20 mL of drug to a 1 L bag gives 1020 mL, not 1000 mL. Small error for one drug, real error once you have added three things.
- Preparing formalin from percentage labels. Commercial formaldehyde stocks may be specified by mass rather than mass/volume, and histopathology requires the correct buffer and safety controls. Use pre-made 10% neutral buffered formalin or a laboratory-validated protocol; this calculator does not provide a formalin preset.
- Diluting with sterile water and giving it intravenously. Sterile water is hypotonic and haemolytic. Use it only when the final solution is isotonic or the route tolerates it.
- Not labelling the syringe. A clear syringe of 0.1 mg/mL adrenaline looks exactly like a clear syringe of 1 mg/mL adrenaline. Label drug, concentration, diluent, date, time and initials every time.
- Assuming the dilution is stable. Diluting removes preservative and changes pH. Unless your practice has validated a longer window, treat a diluted product as single use and discard what you do not give.
- Diluting things that should not be diluted. Propofol emulsions, some suspensions and several long-acting products lose stability or separate when diluted. Check the label first.
Frequently asked questions
C1V1 = C2V2. Rearranged for the volume of stock you need, V1 = (C2 × V2) ÷ C1. Subtract V1 from V2 to get the diluent volume.
One part stock to nine parts diluent. Take 1 mL of the drug and add 9 mL of diluent to make 10 mL total. The final concentration is one tenth of the original. A 1 in 10 dilution is not one part drug to ten parts diluent, which would be a 1 in 11.
1:1000 adrenaline is 1 mg/mL and 1:10,000 is 0.1 mg/mL, so it is a 1 in 10 dilution. Draw 1 mL of adrenaline into a 10 mL syringe and fill to 10 mL with 0.9% sodium chloride. Label it immediately, because the two strengths are indistinguishable once drawn up.
A 2% weight-per-volume solution is 20 mg/mL. Multiply by 10 only when the label explicitly states % w/v; do not use that shortcut for % w/w or % v/v.
For a potassium-free bag, multiply the target concentration by the actual or protocol-approved bag volume, then divide by the stock concentration. For 20 mEq/L in an actual 1 L bag from a 2 mEq/mL vial, that is 10 mL. Remove the same volume first if the bag must remain at 1000 mL, then invert it several times. Lactated Ringer's already contains potassium and must not use this zero-background example; use a validated total-potassium protocol instead.
Use one or more staged 1-in-10 dilutions: at each stage, mix 1 mL of the previous solution with 9 mL of compatible diluent. The calculator repeats those bounded steps until the final draw is above your clinic threshold and fits the requested preparation. Never estimate between device graduations, and account for needle and hub dead space in very small patients.
Yes. In C1V1 = C2V2, V2 is the total finished volume including the drug. If you want 10 mL of a diluted solution and the maths says 1 mL of drug, you add 9 mL of diluent, not 10 mL.
Often yes, and for small patients it is the safer option because it turns an unmeasurable volume into a measurable one. But check compatibility with the diluent, check that the product is a solution rather than an emulsion or suspension, and use it promptly. Some products precipitate, separate or lose potency once diluted.
A 1 in 10 dilution describes a relationship to whatever you started with, so its final strength depends entirely on the stock. A 10% solution is an absolute concentration, 100 mg/mL. Diluting a 50% solution 1 in 10 gives 5%, not 10%.
Treat it as immediate use unless you have a validated stability figure. Dilution alters pH, dilutes any preservative and introduces a contamination risk at the point of preparation. Many practices discard diluted syringes at the end of the procedure or the shift. Follow your own protocol and the product label.
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