McFarland Standard Adjustment Calculator

About McFarland Standard Adjustment Calculator

Diluent needed to bring a suspension to a target turbidity. The McFarland Standard Adjustment Calculator on Picscaler gives you the answer instantly in your browser, with no sign-up.

Inputs: Measured turbidity (McFarland), Target turbidity (McFarland) and Suspension volume (mL). Results shown: Diluent to add, Final volume and Approx. CFU/mL at target.

Formula: Diluent = volume x (measured / target - 1); approximate CFU/mL = McFarland x 3 x 10^8. 0.5 McFarland is about 1.5 x 10^8 CFU/mL for E. coli; it varies by organism.

This tool is for education and information. It does not replace clinical judgement, so confirm results against your laboratory's reference ranges and local guidelines.

How to use McFarland Standard Adjustment Calculator

1. Enter Measured turbidity (McFarland), Target turbidity (McFarland) and Suspension volume (mL).
2. Press Calculate.
3. Read Diluent to add, Final volume and Approx. CFU/mL at target in the result table.
4. Use the formula and notes under the result to check the working.

Frequently asked questions

Is McFarland Standard Adjustment Calculator free?

Yes. McFarland Standard Adjustment Calculator is completely free to use on Picscaler.

Do I need to create an account?

No. You can use it straight away without signing up.

Is my data safe?

Your input is processed in your browser on your own device and is not uploaded to Picscaler.

Can I use it for medical decisions?

No. It is an educational aid and does not replace professional medical judgement.