Nursing math
Dosage calculation practice
Type each line of your dimensional analysis, units and all. Lemma checks the arithmetic exactly, checks the units on every part that has them, and names the mistake when something is off.
Practice only, not clinical advice. Made-up numbers for arithmetic practice. Never use this page to work out a real dose.
Try one
Practice only, not clinical advice.
An order reads 300 mg by mouth. The oral liquid on hand is labelled 100 mg per 5 mL. How many mL are given?
- Rounding rule: Round your final answer to the nearest tenth, and only at the last step; keep full precision until then. (This one comes out even.)
- Conversions: Use 1 g = 1000 mg, 1 mg = 1000 mcg, 1 L = 1000 mL, 1 hr = 60 min, 1 kg = 2.2 lb, 1 tsp = 5 mL, 1 tbsp = 15 mL and 1 fl oz = 30 mL.
- Final unit: mL. Write each line with its units.
Go to the full practice test (33 problems)
What the checker does
- Reads quantities and units (mcg, mg, g, kg, lb, mL, L, tsp, tbsp, gtt, units, mEq, tablets, capsules, hr, min, and compounds like mg/kg, mL/hr and mcg/kg/min).
- Does the arithmetic with exact fractions, never rounded decimals, and checks each line equals the answer in value and in dimension, with the units cancelling.
- Gives one of three outcomes per line: correct, a named error, or can’t check. A line it cannot read is never passed.
- Says what it did not check. If a number is written without a unit, or a setup uses numbers that don’t match the problem’s, the line can match the answer and still be marked partly verified.
- Holds you to the rounding rule written in the problem. It never assumes one.
The mistakes it names
| Error | What it means |
|---|---|
| A factor-of-1000 slip | A slip between mcg, mg, g or kg. |
| A decimal slip | The right digits with the decimal point in the wrong place. |
| An upside-down fraction | A fraction (strength, conversion) written upside down. |
| Pounds and kilograms converted the wrong way | Multiplying by 2.2 where you should divide, or the reverse. |
| An hours and minutes slip | A missed or misplaced 60 between hours and minutes. |
| The wrong drop factor | A drop factor that is not the one the problem gives. |
| The units do not cancel | The units left over are not the units you wanted. |
| The answer has no unit | A final answer with a number and no unit. |
| Not the unit that was asked for | The right amount, written in a different unit than asked. |
| Right number, wrong unit | The number matches but the unit is wrong. |
| Not rounded as the problem says | Not rounded the way the problem says to round. |
| Rounded the wrong way | Rounded in the wrong direction or to the wrong place. |
| Rounded too early | Rounded in the middle of the work instead of at the end. |
| A trailing zero | Writing 5.0 where 5 is meant. |
| A missing leading zero | Writing .5 where 0.5 is meant. |
| A fraction of a tablet that cannot be given | A fraction of a tablet or capsule that cannot be given. |
| An unsafe abbreviation | U, IU or cc in place of units or mL. |
Problem types
- Oral tablets and capsules5 problems
- Oral liquids6 problems
- Weight-based doses5 problems
- IV rate in mL/hr4 problems
- IV drops per minute4 problems
- Infusion time3 problems
- Titration in mcg/kg/min3 problems
- Reconstitution3 problems
Units and conventions used here
| Conversion | Value |
|---|---|
| Mass | 1 g = 1000 mg, 1 mg = 1000 mcg |
| Volume | 1 L = 1000 mL |
| Time | 1 hr = 60 min |
| Body weight | 1 kg = 2.2 lb (the value these problems use; your program may use another) |
Lemma treats U, IU and cc, a trailing zero (5.0) and a missing leading zero (.5) as errors rather than accepting them quietly. Your program’s own rules come first.
Also on Lemma
- Dosage proportionsRatios, weight conversion and supply duration
- Unit conversionsConvert between units step by step
Questions
What Lemma stores and why: privacy.
Is this clinical advice?
No. Every problem uses made-up numbers for arithmetic practice, and no number on these pages is a recommendation for any real person or medication. Never use this page to work out a real dose; follow your program's rules and your facility's policies.
What does "can't check this line" mean?
The checker has three outcomes: correct, a named error, or can't check. If a line cannot be read (a unit it does not know, a bare number at the end, an unclear fraction), it is never passed. It is returned to you with the reason so you can rewrite it. A line that matches the answer can still be marked partly verified when a number has no unit or the setup uses numbers that don't match the problem's.
Why does each problem state a rounding rule?
Rounding rules differ between programs, so Lemma never assumes one. Each problem tells you how to round and when, and the checker holds you to that rule.
Which kg to lb conversion is used?
These problems use 1 kg = 2.2 lb and say so in the problem. Some programs use a different value; if yours does, use your program's value in your own work.
Do I need an account? What is sent about my work?
No account. The checker runs in your browser, and nothing you type is stored or sent: not your lines, not the problem's numbers. Lemma does send a few Google Analytics events from this site, and Google Analytics sets its own cookie, so they are counts, not a promise of anonymity. They are: dosage_problem_started (the problem type, such as oral or IV); dosage_check_used (the problem type, whether it was a final answer, the outcome: correct, partly verified, error or can't check, and for an error its name, such as inverted-ratio); dosage_problem_finished (the problem type, whether the work was fully or partly verified, whether you used a hint, the number of wrong lines and of checks); and dosage_set_finished (which set you finished, with counts of problems solved clean, with help and partly verified). Which problems you solved is kept in this browser only.
Content written 2026-11-03. Independent practice, not affiliated with any school, exam or publisher.